Split (1)

train · 127k rows

text large_stringlengths 7 3.02k
Azulene is a prototypical molecule with an anomalous fluorescence from the second excited electronic state, thus violating Kasha's rule, and with an emission spectrum that cannot be understood within the Condon approximation. To better understand photophysics and spectroscopy of azulene and other non-conventional ...
Symmetry considerations are at the core of the major frameworks used to provide an effective mathematical representation of atomic configurations that is then used in machine-learning models to predict the properties associated with each structure. In most cases, the models rely on a description of atom-centered envir...
Mesoscopic $N-$atom systems derive their structural and dynamical properties from processes coupled across multiple scales in space and time. An efficient method for understanding these systems in the friction dominated regime from the underlying N-atom formulation is presented.
A circularly polarized laser pulse can induce persistent intra-molecular currents by either exciting or ionizing molecules. These two cases are identified as electron currents and hole currents, respectively, and up to now they have been studied only separately.
Biomolecules couple to their aqueous environment through a variety of noncovalent interactions. Local structures at the surface of DNA and RNA are frequently determined by hydrogen bonds with water molecules, complemented by non-specific electrostatic and many-body interactions.
We consider a 3-dimensional lattice model of a network-forming fluid, which has been recently investigated by Girardi and coworkers by means of Monte Carlo simulations [J. Chem.
The dynamics of many-body fermionic systems are important in problems ranging from catalytic reactions at electrochemical surfaces, to transport through nanojunctions, and offer a prime target for quantum computing applications. Here we derive the set of conditions under which fermionic operators can be exactly replac...
We investigate entirely electronic torsional vibrational modes in linear cumulene chains. The carbon nuclei of a cumulene are positioned along the primary axis so they can participate only in transverse and longitudinal motions.
The zigzag edge of a graphene nanoribbon possesses a unique electronic state that is near the Fermi level and localized at the edge carbon atoms. We investigate the chemical reactivity of these zigzag edge sites by examining their reaction energetics with common radicals from first principles.
The presence of solvent tunes many properties of a molecule, such as its ground and excited state geometry, dipole moment, excitation energy, and absorption spectrum. Because the energy of the system will vary depending on the solvent configuration, explicit solute-solvent interactions are key to understanding solutio...
This article presents chemical analysis of jet fuel (Jet A-1) heteroatomic fuel components with identification of an antioxidant lichen substance in methanol extracted fuel samples. Thermal stressing of jet fuel produces soluble macromolecular oxidatively reactive species (SMORS) and heteroatomic deposits.
Dimers of carbon disulfide (CS$_2$) molecules embedded in helium nanodroplets are aligned using a moderately intense, 160ps, non-resonant, circularly polarized laser pulse. It is shown that the intermolecular carbon-carbon (C-C) axis aligns along the axis perpendicular to the polarization plane of the alignment laser ...
We present a new program implementation of the gaussian process regression adaptive density-guided approach [J. Chem. Phys. 153 (2020) 064105] in the MidasCpp program. A number of technical and methodological improvements made allowed us to extend this approach towards calculations of larger molecular systems than tho...
For the design and optimization of CO2 recovery from alcoholic fermentation processes by distillation, models for vapor-liquid equilibria (VLE) are needed. Two such thermodynamic models, the Peng-Robinson equation of state (EOS) and a model based on Henry's law constants, are proposed for the ternary mixture N2+O2...
Recent first-principle calculations unveiled a distinctive dynamic behavior in water molecule rotation during the melting process of highly confined water, indicating a notable time-scale separation in diffusion. In this short paper, we conducted molecular dynamics (MD) simulations to explore the rotation dynamics dur...
Pyrene-functionalized materials are extensively employed in photoluminescent applications, owing to their extended pi-conjugation and favorable photophysical properties. However, their luminescent performance is often attenuated by pi-pi stacking-driven excimer formation and molecular oxygen quenching.
We present the ProCS method for the rapid and accurate prediction of protein backbone amide proton chemical shifts - sensitive probes of the geometry of key hydrogen bonds that determine protein structure. ProCS is parameterized against quantum mechanical (QM) calculations and reproduces high level QM results obtained...
Collisional complexes, which are formed as intermediate states in molecular collisions, are typically short-lived and decay within picoseconds. However, in ultracold collisions involving bialkali molecules, complexes can live for milliseconds, completely changing the collision dynamics.
Typically, a Lewis acid and a base react with each other and form classic acid base adducts. The neutralization reaction is however prevented by the introduction of bulky substitutes and this interesting finding leads to a new concept called frustrated Lewis pairs, FLPs.
The binding energies of argon dimer are calculated by solving the homogeneous Lippmann-Schwinger integral equation in momentum space. Our numerical analysis using two models of argon-argon interaction developed by Patkowski {\it et al.
Two-dimensional electronic spectroscopy has become one of the main experimental tools for analyzing the dynamics of excitonic energy transfer in large molecular complexes. Simplified theoretical models are usually employed to extract model parameters from the experimental spectral data.
Conical intersections between electronic states often dictate the chemistry of photoexcited molecules. Recently developed sources of ultrashort extreme ultraviolet (XUV) pulses tuned to element-specific transitions in molecules allow for the unambiguous detection of electronic state-switching at a conical intersection...
We present the computational methodology which for the first time allows rigorous twelve-dimensional (12D) quantum calculations of the coupled intramolecular and intermolecular vibrational states of hydrogen-bonded trimers of flexible diatomic molecules. Its starting point is the approach that we introduced recently f...
We simulate the long-range inter-complex electronic energy transfer in Photosystem II -- from the antenna complex, via a core complex, to the reaction center -- using a non-Markovian (ZOFE) quantum master equation description that allows us to quantify the electronic coherence involved in the energy transfer. We ident...
Many atomic liquids can form transient covalent bonds reminiscent of those in the corresponding solid states. These directional interactions dictate many important properties of the liquid state, necessitating a quantitative, atomic-scale understanding of bonding in these complex systems.
Porous graphene has high mechanical strength and atomic layer thickness, which make it a promising material for material separation and biomolecule sensing. Electrostatic interactions between charges in aqueous solution are a kind of strong long-range interaction which may have great influence on the fluid transport t...
Amino acids and other small chiral molecules play key roles in biochemistry. However, in order to understand how these molecules behave in vivo, it is necessary to study them under aqueous-phase conditions.
Understanding the performance of machine learning algorithms is essential for designing more accurate and efficient statistical models. It is not always possible to unravel the reasoning of neural networks.
Due to current technological challenges, including the complexity of precise control, low long-term survival and success rates, difficulty in maintaining function over extended periods, and high energy consumption, the construction of life-like creatures with multilevel structures and varied physiological characteristi...
A challenge for molecular quantum dynamics (QD) calculations is the curse of dimensionality with respect to the nuclear degrees of freedom. A common approach that works especially well for fast reactive processes is to reduce the dimensionality of the system to a few most relevant coordinates.
Free energy perturbation (FEP) is frequently used to evaluate the free energy change of a biological process, e.g. the drug binding free energy or the ligand solvation free energy. Due to the sampling inefficiency, FEP is often employed together with computationally expensive enhanced sampling methods.
A simple and non-destructive method for identification of a single molecular ion sympathetically cooled by a single laser cooled atomic ion in a linear Paul trap is demonstrated. The technique is based on a precise determination of the molecular ion mass through a measurement of the eigenfrequency of a common motional...
In this paper, we address the challenge of obtaining a comprehensive and symmetric representation of point particle groups, such as atoms in a molecule, which is crucial in physics and theoretical chemistry. The problem has become even more important with the widespread adoption of machine-learning techniques in scien...
Extensive research has been carried out in the past to estimate the bulk viscosity of dense monatomic fluids; however, little attention has been paid to estimate the same in the dilute gas regime. In this work, we perform precise Green-Kubo calculations in molecular dynamics simulations to estimate the bulk viscosity ...
We have applied path integral simulations, in combination with new ab initio based water potentials, to investigate nuclear quantum effects in liquid water. Because direct ab initio path integral simulations are computationally expensive, a flexible water model is parameterized by force-matching to density functional ...
The successful application of machine learning (ML) in catalyst design relies on high-quality and diverse data to ensure effective generalization to novel compositions, thereby aiding in catalyst discovery. However, due to complex interactions, catalyst design has long relied on trial-and-error, a costly and labor-int...
The anaerobic co-digestion of slaughterhouse wastewater and food waste offers a sustainable approach to waste treatment and biogas production. However, limited literature was found on the study of ferric oxide as conductive material in co-digestion of the two substrates.
The radiolysis of water is an important study in microdosimetry, one of the resulting and important molecules in this study is the $OH^-$. Theoretical quantum mechanics calculations are used to obtain the differential cross section for the elastic collision, first excited state and ionization of water molecule.
We revisit classical nucleation theory (CNT) for the homogeneous bubble nucleation rate and improve the classical formula using a new prefactor in the nucleation rate. Most of the previous theoretical studies have used the constant prefactor determined by the bubble growth due to the evaporation process from the bubbl...
CH3NH3PbI3-based solar cells were characterized with electron beam-induced current (EBIC), and compared to CH3NH3PbI3-xClx ones. A spatial map of charge separation efficiency in working cells shows p-i-n structures for both thin film cells.
The current state of the art in direct water splitting in photo-electrochemical cells (PECs) is presented together with: (i) a case study of water splitting using a simple solar cell with the most efficient water splitting electrodes and
We computationally investigate the chronoamperometric current response of spherical and cubic particles on a supporting insulating surface. By using the method of finite differences and random walk simulations, we can show that both systems exhibit identical responses on all time scales if their exposed surface areas ...
The effervescence and the stability of the ring of fine bubbles crowning the surface of a champagne glass, the "collar", constitute one of the hallmarks of Champagne. Defects in the stability of this collar are not well understood and account for a significant proportion of bottle return.
We introduce the coherent state mapping ring-polymer molecular dynamics (CS-RPMD), a new method that accurately describes electronic non-adiabatic dynamics with explicit nuclear quantization. This new approach is derived by using coherent state mapping representation for the electronic degrees of freedom (DOF) and the...
Numerical calculations of the effect of organophosphorous inhibitor (CF3CH2O)3P and its mixtures with carbon dioxide on propane flames are carried out using the three dimensional Reynolds-averaged Navier-Stokes (RANS) equations in the low Mach number approximation. The k-e model of turbulence, the EDC combustion model...
The remarkable rotational symmetry of the photosynthetic antenna complexes of purple bacteria has long been thought to enhance their light harvesting and excitation energy transport. We study the role of symmetry by modeling hypothetical antennas whose symmetry is broken by altering the orientations of the bacteriochl...
We have performed Fourier transform microwave spectroscopy of benzonitrile, without and with applied electric fields. From the field-free hyperfine-resolved microwave transitions we simultaneously derive accurate values for the rotational constants, centrifugal distortion constants, and nitrogen nuclear quadrupole cou...
We consider the sampling of the coupled cluster expansion within stochastic coupled cluster theory. Observing the limitations of previous approaches due to the inherently non-linear behaviour of a coupled cluster wavefunction representation we propose new approaches based upon an intuitive, well-defined condition for ...
The nature of mobility of ions and water molecules in dilute aqueous solutions of electrolytes (at most fifteen water molecules per ion) is investigated. It is shown that the behavior of the mobility coefficients of water molecules and ions, as well as the self-diffusion coefficients of water molecules, are determined...
New ab-initio surface hopping simulations of the excited state dynamics of CS$_2$ including spin-orbit coupling are compared to new experimental measurements using a multiphoton ionisation probe in a photoelectron spectroscopy experiment. The calculations highlight the importance of the triplet states even in the very...
Selecting distinct quantum pathways in two-dimensional electronic spectroscopy (2DES) can give particularly deep insights into coherent and incoherent interactions and quantum dynamics in various materials. This includes isolating rephasing and non-rephasing pathways for conventional single-quantum 2DES, but also the ...
Interacting dipole ($p$) bosons along with scalar ($s$) bosons, based on the ideas drawn from the interacting boson model of atomic nuclei, led to the development of the vibron model based on $U(4)$ spectrum generating algebra for diatomic molecules. The $U(4) \supset SO(4) \supset SO(3)$ algebra generates rotation-vi...
Metal-organic frameworks (MOFs) marry inorganic nodes, organic edges, and topological nets into programmable porous crystals, yet their astronomical design space defies brute-force synthesis. Generative modeling holds ultimate promise, but existing models either recycle known building blocks or are restricted to small...
We present experiments in which an ultra-cold sample of ammonia molecules is released from an electrostatic trap and recaptured after a variable time. It is shown that, by performing adiabatic cooling before releasing the molecules and adiabatic re-compression after they are recaptured, we are able to observe molecule...
This work develops and illustrates a new method of calculating "chemically accurate" electronic wavefunctions (and energies) via a truncated full configuration interaction (CI) procedure which arguably circumvents the large matrix diagonalization that is the core problem of full CI and is also central to modern...
The rovibrational electric dipole transitions in the ground electronic state of the HD molecule are studied. A simple, yet rigorous formula is derived for the transition rates in terms of the electric dipole moment function $D(R)$, which is calculated in a wide range of $R$.
An effective Hamiltonian without symmetry restriction has been developed to model the rotational and fine structure of two nearly degenerate electronic states of an open-shell molecule. In addition to the rotational Hamiltonian for an asymmetric top, this spectroscopic model includes energy separation between the two ...
We study the spectra of the molecular orbital Hessian (stability matrix) and random-phase approximation Hamiltonian of broken-symmetry Hartree-Fock solutions, focusing on zero eigenvalue modes. After all negative eigenvalues are removed from the Hessian by following their eigenvectors downhill, one is left with only p...
In view of clean environment, the industry needs to address multiple demands at different levels of production and processes via the sustainable approach including recycling or smart use of produced waste. On the other hand, a development and success of green energy requires the crucial materials synthesized via effic...
We present a new application of the Generator Coordinate Method (GCM) as an electronic structure method for strong electron correlation in molecular systems. We identify spin fluctuations as an important generator coordinate responsible for strong static electron correlation that is associated with bond-breaking proce...
We study the Wasserstein metric to measure distances between molecules represented by the atom index dependent adjacency "Coulomb" matrix, used in kernel ridge regression based supervised learning. Resulting quantum machine learning models exhibit improved training efficiency and result in smoother predictions...
The role of numerical accuracy in training and evaluating neural network-based potential energy surfaces is examined for different experimental observables. For observables that require third- and fourth-order derivatives of the total energy with respect to Cartesian coordinates single-precision arithmetics as is typi...
More than half of the waste heat rejected into the environment has temperatures lower than 100 $^\circ C$, which accounts for nearly 85 PWh/year worldwide. Efficiently harvesting low-grade heat could be a promising step toward carbon neutrality.
Quantum mechanics describes the unitary time evolution of closed systems. In practice, every quantum system interacts with the environment leading to an irreversible loss of coherence.
The dimensionless zero-frequency intrinsic second hyperpolarizability \gamma_{int}=\gamma/4E_{10}^{-5}m^{-2}(e\hbar)^{4} was optimized for a single electron in a 1D well by adjusting the shape of the potential. Optimized potentials were found to have hyperpolarizabilities in the range -0.15\lessapprox\gamma_{int}\less...
This work introduces various approaches to include connected three-body terms in unitary many-body theories, focusing a representative example on the driven similarity renormalization group (DSRG). Starting from the least approximate method - the linearized DSRG truncated to one-, two-, and three-body operators [LDSRG...
Quantitative fluorescence analysis is often used to derive chemical properties, including stoichiometries, of biomolecular complexes. One fundamental underlying assumption in the analysis of fluorescence data -- whether it be the determination of protein complex stoichiometry by super-resolution, or step-counting by p...
Time-resolved spectroscopy provides the main tool for analyzing the dynamics of excitonic energy transfer in light-harvesting complexes. To infer time-scales and effective coupling parameters from experimental data requires to develop numerical exact theoretical models.
The practical utility of Møller-Plesset (MP) perturbation theory is severely constrained by the use of Hartree-Fock (HF) orbitals. It has recently been shown that use of regularized orbital-optimized MP2 orbitals and scaling of MP3 energy could lead to a significant reduction in MP3 error (J. Phys. Chem. Lett. 10, 417...
A new difference-frequency method based on electro-optic phase modulators and two free-running lasers is reported to perform THz dual-comb spectroscopy.
We develop a systematic study of Jahn-Teller (JT) models with continuous symmetries by explor- ing their algebraic properties. The compact symmetric spaces corresponding to JT models carrying a Lie group symmetry are identified, and their invariants used to reduce their adiabatic potential energy surfaces into orbit s...
A major goal of many spectroscopic techniques is to provide comprehensive information on the local chemical environment. Electron transfer mediated decay (ETMD) is a sensitive probe of the environment since it is actively involved in this non-local radiationless decay process through electron and energy transfer steps...
The formation of $\mbox{O}_2$ by radiative association and by inverse predissociation of ground state oxygen atoms is studied using quantum-mechanical methods. Cross sections, emission spectra, and rate coefficients are presented and compared with prior experimental and theoretical results.
In this work, the Z-average, effective, apparent diffusion coefficients and their poly-dispersity indexes were investigated for dilute poly-disperse homogeneous spherical particles in dispersion where the Rayleigh-Gans-Debye approximation is valid. The results reveal that the values of the apparent and effective diffu...
Polaritonic chemistry relies on the strong light-matter interaction phenomena for altering the chemical reaction rates inside optical cavities. To explain and to understand these processes, the development of reliable theoretical models is essential.
The effects of pH, ionic strength and temperature on sorption of Eu(III) on attapulgite were investigated in the presence and absence of fulvic acid (FA) and humic acid (HA). The results indicated that the sorption of Eu(III) on attapulgite was strongly dependent on pH and ionic strength, and independent of temperatur...
Hydrogen transport in the anode of a proton-exchange membrane fuel cell (PEMFC) has been studied with a modulation technique relating the hydrogen flow-rate $(\tilde{Q}_{H2})$ and the faradaic current $(\tilde{I})$, called $\textit{Current-modulated Hydrogen flow-rate Spectroscopy}$ (CH2S). A simple analytical express...
In this paper, we revisit the concepts of the reactivity map and the reactivity bands as an alternative to the use of perturbation theory for the determination of the phase space geometry of chemical reactions. We introduce a reformulated metric, called the asymptotic trajectory indicator, and an efficient algorithm t...
The phenomenon of orbital relaxation upon excitation of core electrons is a major problem in the linear-response treatment of core-hole spectroscopies. Rather than addressing relaxation through direct dynamical correlation of the excited state via equation-of-motion coupled cluster theory (EOMEE-CC), we extend the alt...
Many enhanced sampling methods, such as Umbrella Sampling, Metadynamics or Variationally Enhanced Sampling, rely on the identification of appropriate collective variables. For proteins, even small ones, finding appropriate collective variables has proven challenging.
The adiabatic approximation in time-dependent density functional theory (TDDFT) yields reliable excitation spectra with great efficiency in many cases, but fundamentally fails for states of double excitation character. We discuss how double-excitations are at the root of some of the most challenging problems for TDDFT...
The manipulation of the motion of neutral molecules with electric or magnetic fields has seen tremendous progress over the last decade. Recently, these techniques have been extended to the manipulation of large and complex molecules.
A novel mediator-free, non-enzymatic electrochemical sensor, based on a graphene-Schottky junction, was fabricated for glucose detection. The sensor offers a promising alternative to the conventional enzyme-catalyzed electrochemical continuous glucose monitoring systems (CGM), as it overcomes many of the drawbacks att...
Whilst the primary bottleneck to a number of computational workflows was not so long ago limited by processing power, the rise of machine learning technologies has resulted in a paradigm shift which places increasing value on issues related to data curation - i.e., data size, quality, bias, format, and coverage. Incre...
We consider a suspended elastic rod under longitudinal compression. The compression can be used to adjust potential energy for transverse displacements from harmonic to double well regime.
We report how the unique temporal and spectral features of pulsed entangled photons from a parametric downconversion source can be utilized for manipulating electronic excitations through the optimization of their spectral phase. A new comprehensive optimization protocol based on Bayesian optimization has been develop...
We presents a fully quantal version of the Langevin model for the total rate of exoergic ion-molecule reactions or inelastic processes. The model, which is derived from a rigorous multichannel quantum-defect formulation of bimolecular processes, agrees with the classical Langevin model at sufficiently high temperature...
The development of ammonia-methane (NH3-CH4) combustion as a hydrogen-carrier energy source faces major challenges such as significant NOx emissions, hindering its practical implementation. This paper examines how ethanol (C2H6O) and methanol (CH4O) additives influence formation pathways of NOx using ReaxFF molecular ...
A new strategy for global geometry optimization of clusters is presented. Important features are a restriction of search space to favorable nearest-neighbor distance ranges, a suitable cluster growth representation with diminished correlations, and easy transferability of the results to larger clusters.
In the self-consistent continuum solvation (SCCS) approach ($\textit{J. Chem.
The analytic gradient theory for both iterative and non-iterative coupled-cluster approximations that include connected quadruple excitations is presented. These methods include, in particular, CCSDT(Q), which is an analog of the well-known CCSD(T) method which starts from the full CCSDT method rather than CCSD.
We present single- and multiple-quantum correlation $J$-spectroscopy detected in zero ($<\! \!
In the present paper we examine the effects of noise on Monte Carlo algorithms, a problem raised previously by Kennedy and Kuti (Phys. Rev. Lett.
We analyze the real-time electron-photon dynamics in long-range polariton-mediated energy transfer using a real-time quantum electrodynamics coupled cluster (RT-QED-CC) model, which allows for spatial and temporal visualization of transport processes. We compute the time evolution of photonic and molecular observables...
We discuss the time-dependent formulation of perturbation theory in the context of the interacting zeroth-order Hamiltonians that appear in multi-reference situations. As an example, we present a time-dependent formulation and implementation of second-order n-electron valence perturbation theory.
This review describes recent experimental and theoretical advances in forming molecules in ultracold gases of trapped alkali metal atoms, both by magnetic tuning through Feshbach resonances and by photoassociation. Molecular Bose-Einstein condensation of long-range states of both boson dimers and fermion dimers was ac...
A semiclassical theory of small oscillations is developed for nuclei that are subject to velocity-dependent forces in addition to the usual interatomic forces. When the velocity-dependent forces are due to a strong magnetic field, novel effects arise -- for example, the coupling of vibrational, rotational, and transla...
The glass transition GT is usually thought of as a structural arrest that occurs during the cooling of a liquid, or sometimes a plastic crystal, trapping a metastable state of the system before it can recrystallize to stabler forms1. This phenomenon occurs in liquids of all classes, most recently in bulk metallic glas...
We extend the frozen density embedding theory to non-integer subsystems' particles numbers. Different features of this formulation are discussed, with special concern for approximate embedding calculations.
By adding a GLPT3 (third-order Görling-Levy perturbation theory, or KS-MP3) term E3 to the XYG7 form for a double hybrid, we are able to bring down WTMAD2 (weighted total mean absolute deviation) for the very large and chemically diverse GMTKN55 benchmark to an unprecedented 1.17 kcal/mol, competitive with much costlie...

Subsets and Splits

No community queries yet

The top public SQL queries from the community will appear here once available.