MIT-OCW-Transcripts / -MJrb7xScbU.txt
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in this demonstration I'm going to show
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in this demonstration I'm going to show
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in this demonstration I'm going to show
you how to construct 2d brilliant zones
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you how to construct 2d brilliant zones
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you how to construct 2d brilliant zones
and hopefully achieve a better
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and hopefully achieve a better
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and hopefully achieve a better
understanding them and what they are so
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understanding them and what they are so
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understanding them and what they are so
a brilliant zone is an important concept
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a brilliant zone is an important concept
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a brilliant zone is an important concept
in material science and solid-state
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in material science and solid-state
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in material science and solid-state
physics
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physics
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physics
alike because it is used to describe the
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alike because it is used to describe the
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alike because it is used to describe the
behavior of an electron in a perfect
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behavior of an electron in a perfect
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behavior of an electron in a perfect
crystal system so what is a brilliant
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crystal system so what is a brilliant
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crystal system so what is a brilliant
zone the Brillion zone is a particular
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zone the Brillion zone is a particular
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zone the Brillion zone is a particular
choice of the unit cell of the
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choice of the unit cell of the
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choice of the unit cell of the
reciprocal lattice is defined as the
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reciprocal lattice is defined as the
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reciprocal lattice is defined as the
riegner Seitz cell of the reciprocal
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riegner Seitz cell of the reciprocal
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riegner Seitz cell of the reciprocal
lattice it is constructed as the set of
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lattice it is constructed as the set of
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lattice it is constructed as the set of
points and closed by the Bragg planes
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points and closed by the Bragg planes
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points and closed by the Bragg planes
the planes perpendicular to a connection
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the planes perpendicular to a connection
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the planes perpendicular to a connection
line from the origin of to each lattice
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line from the origin of to each lattice
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line from the origin of to each lattice
point passing through the midpoint
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point passing through the midpoint
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point passing through the midpoint
alternatively it is defined as the set
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alternatively it is defined as the set
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alternatively it is defined as the set
of points closer to the origin than to
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of points closer to the origin than to
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of points closer to the origin than to
any other reciprocal lattice point the
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any other reciprocal lattice point the
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any other reciprocal lattice point the
whole reciprocal space may be covered
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whole reciprocal space may be covered
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whole reciprocal space may be covered
without overlap with copies of such
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without overlap with copies of such
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without overlap with copies of such
brilliant zone okay so that was a rather
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brilliant zone okay so that was a rather
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brilliant zone okay so that was a rather
convoluted definition let's do it again
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convoluted definition let's do it again
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convoluted definition let's do it again
let's brush up and be sure that we
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let's brush up and be sure that we
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let's brush up and be sure that we
understand this definition we're going
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understand this definition we're going
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understand this definition we're going
to define her the reciprocal space the
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to define her the reciprocal space the
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to define her the reciprocal space the
Bragg planes as well but it's fine both
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Bragg planes as well but it's fine both
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Bragg planes as well but it's fine both
of these will also do a quick revision
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of these will also do a quick revision
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of these will also do a quick revision
of what is there a record lattice so
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of what is there a record lattice so
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of what is there a record lattice so
that we can go from there to the
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that we can go from there to the
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that we can go from there to the
reciprocal lattice the microscopic
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reciprocal lattice the microscopic
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reciprocal lattice the microscopic
perfect crystal is formed by adding
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perfect crystal is formed by adding
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perfect crystal is formed by adding
identical building blocks so to say unit
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identical building blocks so to say unit
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identical building blocks so to say unit
cells consisting of atoms and groups of
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cells consisting of atoms and groups of
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cells consisting of atoms and groups of
atoms a unit cell is the smallest
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atoms a unit cell is the smallest
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atoms a unit cell is the smallest
component of a crystal that one stacked
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component of a crystal that one stacked
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component of a crystal that one stacked
together with pure translational
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together with pure translational
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together with pure translational
repetition reproducing the whole crystal
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repetition reproducing the whole crystal
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repetition reproducing the whole crystal
which essentially means that you can
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which essentially means that you can
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which essentially means that you can
take the same thing over and over and
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take the same thing over and over and
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take the same thing over and over and
over again and get the whole system done
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over again and get the whole system done
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over again and get the whole system done
so and the groups of atoms these unit
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so and the groups of atoms these unit
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so and the groups of atoms these unit
cells that form the microscopic crystal
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cells that form the microscopic crystal
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cells that form the microscopic crystal
but infinite repetition is called the
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but infinite repetition is called the
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but infinite repetition is called the
basis okay that seems quite clear and
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basis okay that seems quite clear and
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basis okay that seems quite clear and
the basis is formed in such a way that
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the basis is formed in such a way that
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the basis is formed in such a way that
it forms the lattice more commonly known
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it forms the lattice more commonly known
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it forms the lattice more commonly known
as the Rivervale at every point of a
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as the Rivervale at every point of a
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as the Rivervale at every point of a
breve lattice is equivalent to every
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breve lattice is equivalent to every
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breve lattice is equivalent to every
other point which means that the
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other point which means that the
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other point which means that the
arrangement atoms and the crystal is the
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arrangement atoms and the crystal is the
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arrangement atoms and the crystal is the
same when viewed from different lattice
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same when viewed from different lattice
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same when viewed from different lattice
points okay that also seems
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points okay that also seems
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points okay that also seems
understandable and you should probably
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understandable and you should probably
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understandable and you should probably
know that by now so any fundamental
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know that by now so any fundamental
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know that by now so any fundamental
lattice must be definable by three
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lattice must be definable by three
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lattice must be definable by three
primitive translational vectors a1 a2
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primitive translational vectors a1 a2
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primitive translational vectors a1 a2
and a3 the combination of these vectors
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and a3 the combination of these vectors
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and a3 the combination of these vectors
is using to find the crystal
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is using to find the crystal
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is using to find the crystal
translational vector R such that R is
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translational vector R such that R is
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translational vector R such that R is
equal to a 1 and 1 plus a 2 and 2 plus a
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equal to a 1 and 1 plus a 2 and 2 plus a
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equal to a 1 and 1 plus a 2 and 2 plus a
3 and 3 where n are just arbitrary
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3 and 3 where n are just arbitrary
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3 and 3 where n are just arbitrary
integers to show that Mark would show
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integers to show that Mark would show
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integers to show that Mark would show
the size of our lattice so when we the
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the size of our lattice so when we the
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the size of our lattice so when we the
crystal lattice is repeated an infinite
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crystal lattice is repeated an infinite
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crystal lattice is repeated an infinite
amount of times to create the perfect
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amount of times to create the perfect
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amount of times to create the perfect
crystal structure and each of those
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crystal structure and each of those
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crystal structure and each of those
lattices are translationally symmetric
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lattices are translationally symmetric
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lattices are translationally symmetric
and the way I'll look at is is that one
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and the way I'll look at is is that one
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and the way I'll look at is is that one
cannot tell their positional in crystal
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cannot tell their positional in crystal
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cannot tell their positional in crystal
structure because every lattice looks
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structure because every lattice looks
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structure because every lattice looks
this ok so now okay so that seems to
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this ok so now okay so that seems to
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this ok so now okay so that seems to
make sense so now let's go through
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make sense so now let's go through
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make sense so now let's go through
reciprocal space okay so every lattice
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reciprocal space okay so every lattice
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reciprocal space okay so every lattice
has a reciprocal lattice associated
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has a reciprocal lattice associated
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has a reciprocal lattice associated
through in crystallography terms the
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through in crystallography terms the
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through in crystallography terms the
reciprocal lattices of the diffraction
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reciprocal lattices of the diffraction
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reciprocal lattices of the diffraction
prior of a crystal or in quantum
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prior of a crystal or in quantum
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prior of a crystal or in quantum
mechanics it's described this k space
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mechanics it's described this k space
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mechanics it's described this k space
with K being 4k wave vectors in 3d
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with K being 4k wave vectors in 3d
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with K being 4k wave vectors in 3d
lattice the vectors would be v1 v2 and
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lattice the vectors would be v1 v2 and
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lattice the vectors would be v1 v2 and
v3 and they can be denoted it as well
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v3 and they can be denoted it as well
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v3 and they can be denoted it as well
look at it just b1 b1 is equals to 2 pi
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look at it just b1 b1 is equals to 2 pi
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look at it just b1 b1 is equals to 2 pi
times the cross product of the vectors
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times the cross product of the vectors
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times the cross product of the vectors
a2 and a3 from our direct lattice
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a2 and a3 from our direct lattice
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a2 and a3 from our direct lattice
divided by the triple cross scalar
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divided by the triple cross scalar
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divided by the triple cross scalar
product of a 1 a 2 and a 3 in which case
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product of a 1 a 2 and a 3 in which case
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product of a 1 a 2 and a 3 in which case
this cross product of a 2 and a 3 is the
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this cross product of a 2 and a 3 is the
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this cross product of a 2 and a 3 is the
area of our vector of our two vectors in
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area of our vector of our two vectors in
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area of our vector of our two vectors in
the triple scalar product is the volume
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the triple scalar product is the volume
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the triple scalar product is the volume
of our system by simplifying it we can
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of our system by simplifying it we can
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of our system by simplifying it we can
just get 2 pi over the height of our
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just get 2 pi over the height of our
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just get 2 pi over the height of our
unit cell or we can put it in this way
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unit cell or we can put it in this way
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unit cell or we can put it in this way
the larger our direct lattice gets the
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the larger our direct lattice gets the
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the larger our direct lattice gets the
smaller and core person or reciprocal
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smaller and core person or reciprocal
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smaller and core person or reciprocal
lattice becomes another observation that
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lattice becomes another observation that
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lattice becomes another observation that
could actually be made by the reciprocal
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could actually be made by the reciprocal
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could actually be made by the reciprocal
lattices that the reciprocal lattice of
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lattices that the reciprocal lattice of
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lattices that the reciprocal lattice of
the reciprocal lattice is the direct
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the reciprocal lattice is the direct
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the reciprocal lattice is the direct
lattice bit okay for simplicity's sake
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lattice bit okay for simplicity's sake
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lattice bit okay for simplicity's sake
let's look at a transformation from 2d
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let's look at a transformation from 2d
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let's look at a transformation from 2d
lattice to a reciprocal lattice okay so
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lattice to a reciprocal lattice okay so
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lattice to a reciprocal lattice okay so
we have a visualization here where we
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we have a visualization here where we
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we have a visualization here where we
can change
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can change
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can change
the length of our X vector indirect
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the length of our X vector indirect
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the length of our X vector indirect
space and the length of our vibrator
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space and the length of our vibrator
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space and the length of our vibrator
indirect space and we can change whether
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indirect space and we can change whether
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indirect space and we can change whether
or not we're seeing this as a direct
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or not we're seeing this as a direct
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or not we're seeing this as a direct
lattice or by pressing this button as a
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lattice or by pressing this button as a
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lattice or by pressing this button as a
reciprocal lattice so as we can see but
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reciprocal lattice so as we can see but
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reciprocal lattice so as we can see but
increasing the length of our direct
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increasing the length of our direct
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increasing the length of our direct
direct vector we change the sizes of our
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direct vector we change the sizes of our
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direct vector we change the sizes of our
reciprocal lattice vectors and the other
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reciprocal lattice vectors and the other
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reciprocal lattice vectors and the other
way around
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okay so now we had a definition of the
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okay so now we had a definition of the
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okay so now we had a definition of the
reciprocal space in the rect space let's
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reciprocal space in the rect space let's
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reciprocal space in the rect space let's
go back to our definition so the first
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go back to our definition so the first
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go back to our definition so the first
brilliant zone can be defined as a set
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brilliant zone can be defined as a set
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brilliant zone can be defined as a set
of points in reciprocal space that can
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of points in reciprocal space that can
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of points in reciprocal space that can
be reached from a specific point of
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be reached from a specific point of
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be reached from a specific point of
origin without crossing any breakpoints
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origin without crossing any breakpoints
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origin without crossing any breakpoints
came so what our Bragg planes a Bragg
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came so what our Bragg planes a Bragg
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came so what our Bragg planes a Bragg
plane or in this case a Bragg line is a
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plane or in this case a Bragg line is a
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plane or in this case a Bragg line is a
Bragg line with perpendicular bisector
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Bragg line with perpendicular bisector
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Bragg line with perpendicular bisector
reciprocal lattice vector a vector which
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reciprocal lattice vector a vector which
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reciprocal lattice vector a vector which
connects two lattice points and the
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connects two lattice points and the
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connects two lattice points and the
closest Bragg planes are essentially
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closest Bragg planes are essentially
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closest Bragg planes are essentially
accosting the Brillion zone now can show
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accosting the Brillion zone now can show
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accosting the Brillion zone now can show
that the Bragg planes for the closest
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that the Bragg planes for the closest
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that the Bragg planes for the closest
neighbors with this being our original
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neighbors with this being our original
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neighbors with this being our original
lattice point these are the four closest
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lattice point these are the four closest
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lattice point these are the four closest
neighbors in a simple I'd say cubic but
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neighbors in a simple I'd say cubic but
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neighbors in a simple I'd say cubic but
it's actually just the square lattice
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it's actually just the square lattice
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it's actually just the square lattice
because it's in 2d and if we add the
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because it's in 2d and if we add the
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because it's in 2d and if we add the
second large vectors before the second
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second large vectors before the second
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second large vectors before the second
closest neighbors you can see these ones
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closest neighbors you can see these ones
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closest neighbors you can see these ones
and essentially conveys the same
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and essentially conveys the same
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and essentially conveys the same
information when we go to a higher order
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information when we go to a higher order
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information when we go to a higher order
of closest neighbors we can see that the
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of closest neighbors we can see that the
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of closest neighbors we can see that the
system gets a lot more complex okay so
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system gets a lot more complex okay so
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system gets a lot more complex okay so
now we've seen what our back planes can
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now we've seen what our back planes can
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now we've seen what our back planes can
go towards brilliant zones so this is
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go towards brilliant zones so this is
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go towards brilliant zones so this is
the first brilliant result it is what it
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the first brilliant result it is what it
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the first brilliant result it is what it
seems it is as you can imagine the Bragg
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seems it is as you can imagine the Bragg
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seems it is as you can imagine the Bragg
planes just go here and the brilliant
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planes just go here and the brilliant
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planes just go here and the brilliant
zone shows us the area in reciprocal
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zone shows us the area in reciprocal
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zone shows us the area in reciprocal
space that is closer to our lattice
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space that is closer to our lattice
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space that is closer to our lattice
point than any other lattice point which
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point than any other lattice point which
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point than any other lattice point which
are essentially the Bragg planes as well
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are essentially the Bragg planes as well
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are essentially the Bragg planes as well
as we can see if our reciprocal lattice
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as we can see if our reciprocal lattice
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as we can see if our reciprocal lattice
origin point isn't here this the square
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origin point isn't here this the square
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origin point isn't here this the square
is closer to this point than to any
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is closer to this point than to any
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is closer to this point than to any
other point and after these lines it
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other point and after these lines it
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other point and after these lines it
gets the other way around
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gets the other way around
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gets the other way around
so we can move on forward to a higher
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so we can move on forward to a higher
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so we can move on forward to a higher
order of brilliant zones
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this is the Brillion zone for the second
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this is the Brillion zone for the second
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this is the Brillion zone for the second
closest neighbor as you can see it it is
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closest neighbor as you can see it it is
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closest neighbor as you can see it it is
rather similar it just takes the second
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rather similar it just takes the second
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rather similar it just takes the second
closest neighbors and essentially draws
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closest neighbors and essentially draws
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closest neighbors and essentially draws
another square it but it's a bit tilted
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another square it but it's a bit tilted
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another square it but it's a bit tilted
to this okay so now let's look at the
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to this okay so now let's look at the
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to this okay so now let's look at the
third one for the third brilliant zone
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third one for the third brilliant zone
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third one for the third brilliant zone
that gets a bit more complex because if
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that gets a bit more complex because if
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that gets a bit more complex because if
we scroll a bit backwards we can see
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we scroll a bit backwards we can see
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we scroll a bit backwards we can see
that the third bread the breakfast for
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that the third bread the breakfast for
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that the third bread the breakfast for
the thirtieth closest neighbors are
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the thirtieth closest neighbors are
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the thirtieth closest neighbors are
these ones so we might think that this
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these ones so we might think that this
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these ones so we might think that this
whole thing would be that brilliant the
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whole thing would be that brilliant the
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whole thing would be that brilliant the
third brilliant look but it's actually
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third brilliant look but it's actually
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third brilliant look but it's actually
not because with every next system it
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not because with every next system it
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not because with every next system it
gets a bit more complex and it's
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gets a bit more complex and it's
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gets a bit more complex and it's
actually taking account both the third
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actually taking account both the third
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actually taking account both the third
right planes and the first ones okay so
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right planes and the first ones okay so
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right planes and the first ones okay so
now let's do another thing let's turn
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now let's do another thing let's turn
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now let's do another thing let's turn
off on that we can see all the Bragg
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off on that we can see all the Bragg
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off on that we can see all the Bragg
planes and turn up another notch okay so
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planes and turn up another notch okay so
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planes and turn up another notch okay so
here we can see that the fourth Brillion
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here we can see that the fourth Brillion
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here we can see that the fourth Brillion
zone gets a lot more complex now we can
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zone gets a lot more complex now we can
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zone gets a lot more complex now we can
see all the Bragg planes for the quite
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see all the Bragg planes for the quite
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see all the Bragg planes for the quite
for the closest neighbors and these
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for the closest neighbors and these
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for the closest neighbors and these
lines could get quite difficult to
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lines could get quite difficult to
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lines could get quite difficult to
understand by drawing themselves but we
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understand by drawing themselves but we
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understand by drawing themselves but we
can help ourselves out with this
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can help ourselves out with this
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can help ourselves out with this
visualization so yeah we can see that
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visualization so yeah we can see that
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visualization so yeah we can see that
they start to interact with each other
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they start to interact with each other
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they start to interact with each other
and thus make a more difficult structure
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and thus make a more difficult structure
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and thus make a more difficult structure
and if we go to the fifth one and see
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and if we go to the fifth one and see
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and if we go to the fifth one and see
show that we can see all the brilliant
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show that we can see all the brilliant
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show that we can see all the brilliant
zones okay so here we can see that it
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zones okay so here we can see that it
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zones okay so here we can see that it
gets becomes quite a nice drawing if we
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gets becomes quite a nice drawing if we
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gets becomes quite a nice drawing if we
were to keep adding them let's just it
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were to keep adding them let's just it
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were to keep adding them let's just it
let's head to the ninth one okay so see
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let's head to the ninth one okay so see
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let's head to the ninth one okay so see
here we can see a high order brilliant
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here we can see a high order brilliant
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here we can see a high order brilliant
zones and it actually looked kind of
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zones and it actually looked kind of
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zones and it actually looked kind of
nice which is also interesting because
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nice which is also interesting because
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nice which is also interesting because
it's also an art form drawing high
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it's also an art form drawing high
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it's also an art form drawing high
drawing high order billion zones
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drawing high order billion zones
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drawing high order billion zones
the higher you go the more complex and
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the higher you go the more complex and
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the higher you go the more complex and
more discrete the system gets in
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more discrete the system gets in
align:start position:0%
more discrete the system gets in
essentially it looks nicer okay so after
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essentially it looks nicer okay so after
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essentially it looks nicer okay so after
looking at this we can get a short
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looking at this we can get a short
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looking at this we can get a short
definition of how to construct to the
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definition of how to construct to the
align:start position:0%
definition of how to construct to the
brilliant zones so enth brilliant zone
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brilliant zones so enth brilliant zone
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brilliant zones so enth brilliant zone
can be defined as the area or volume if
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can be defined as the area or volume if
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can be defined as the area or volume if
we look in 3d in reciprocal space that
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we look in 3d in reciprocal space that
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we look in 3d in reciprocal space that
can be reached from the origin but
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can be reached from the origin but
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can be reached from the origin but
crossing exactly n minus one Bragg
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crossing exactly n minus one Bragg
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crossing exactly n minus one Bragg
planes
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planes
align:start position:0%
planes
so we can look also add a brilliant zone
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so we can look also add a brilliant zone
align:start position:0%
so we can look also add a brilliant zone
for a system where the atoms are not
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for a system where the atoms are not
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for a system where the atoms are not
perfectly in the perfect square lattice
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perfectly in the perfect square lattice
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perfectly in the perfect square lattice
but are offset a bit making sort of say
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but are offset a bit making sort of say
align:start position:0%
but are offset a bit making sort of say
a triangular lattice and as we can see
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a triangular lattice and as we can see
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a triangular lattice and as we can see
here the first billion zone is it such
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here the first billion zone is it such
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here the first billion zone is it such
such a hexagon and the second one
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such a hexagon and the second one
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such a hexagon and the second one
already gets a bit more difficult by
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already gets a bit more difficult by
align:start position:0%
already gets a bit more difficult by
forming a star shape and the third one
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forming a star shape and the third one
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forming a star shape and the third one
is again so to say FX agon and it goes
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is again so to say FX agon and it goes
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is again so to say FX agon and it goes
on like that
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on like that
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on like that
okay so and then so what information is
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okay so and then so what information is
align:start position:0%
okay so and then so what information is
the brilliance don't hold on what does
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the brilliance don't hold on what does
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the brilliance don't hold on what does
it give us the short vectors in the
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it give us the short vectors in the
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it give us the short vectors in the
Brillion zone or on its boundary
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Brillion zone or on its boundary
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Brillion zone or on its boundary
characterized States in a system with
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characterized States in a system with
align:start position:0%
characterized States in a system with
lattice period periodicity for example
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lattice period periodicity for example
align:start position:0%
lattice period periodicity for example
phone out or or electron state but for
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phone out or or electron state but for
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phone out or or electron state but for
that the whole of the video thanks and
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that the whole of the video thanks and
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that the whole of the video thanks and
this code for this demonstration was
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this code for this demonstration was
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this code for this demonstration was
taken and editors from Mathematica
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taken and editors from Mathematica
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taken and editors from Mathematica
demonstration since made by their slope
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demonstration since made by their slope
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demonstration since made by their slope
cloth