| --- |
| title: Induced-Moment Exchange Explorer |
| emoji: 🧲 |
| colorFrom: indigo |
| colorTo: green |
| sdk: gradio |
| sdk_version: 5.50.0 |
| python_version: "3.10" |
| app_file: app.py |
| license: gpl-3.0 |
| fullWidth: true |
| short_description: Explore UppASD exchange, induced moments, and magnons. |
| --- |
| |
| # Induced-Moment Exchange Explorer |
|
|
| Induced-Moment Exchange Explorer is a Python library and Gradio application for |
| analysing atomistic exchange models supplied in UppASD-style input files. It |
| keeps the supplied exchange data explicit, evaluates reciprocal-space exchange, |
| models selected sites as instantaneous induced moments, downfolds those sites, |
| and calculates collinear-FM magnon diagnostics. |
|
|
| The project is intended for transparent model analysis. It does not infer an |
| electronic susceptibility from a conventional `Jij` file or silently repair |
| incomplete exchange input. |
|
|
| ## UppASD Hamiltonian convention |
|
|
| The native convention is the literal UppASD scalar-Heisenberg `jfile` |
| convention: |
|
|
| ```text |
| H = - sum_(i != j) Jij e_i · e_j |
| ``` |
|
|
| The sum is over ordered pairs, so a pair-complete file contains both `(i,j)` |
| and `(j,i)`. Positive `Jij` is ferromagnetic. The parser stores the numerical |
| `jfile` values unchanged, `J(q)` is the Fourier transform of those literal |
| values, and exported dressed `jfile` values use the same convention without a |
| factor-of-two conversion. |
|
|
| The factor ledger is: |
|
|
| | quantity | factor | origin | |
| |---|---:|---| |
| | `J(q)` | `1` | literal `jfile` Fourier transform | |
| | local exchange field | `2` | derivative of the ordered-pair Hamiltonian | |
| | magnon energy | `2*g` | ordered-pair curvature times one gyromagnetic/Landé factor | |
| | global pair energy | ordered-pair sum | native UppASD convention | |
| | thermal white-noise factor | `2` | fluctuation-dissipation normalization; unrelated to pair counting | |
|
|
| For a different source convention, convert at the boundary with |
| `convert_exchange_to_uppasd`: a single-counted pair Hamiltonian |
| `-sum_<ij> J' e_i·e_j` and a `-1/2` ordered double sum both use |
| `J_UppASD = J'/2` (or `J''/2`). An AF-positive ordered convention requires a |
| sign change. A spin-`S` Hamiltonian written with unit directions first absorbs |
| the spin magnitudes into its pair coefficient and then applies the same |
| single-counted conversion. |
|
|
| ## Start here |
|
|
| Run the application locally: |
|
|
| ```bash |
| python -m pip install -r requirements.txt |
| python app.py |
| ``` |
|
|
| For library-only work, install the package and run the input inspector: |
|
|
| ```bash |
| python -m pip install -e . |
| induced-exchange-uppasd examples/fept_style/inpsd.dat |
| ``` |
|
|
| The application includes small CPU-friendly examples under `examples/`. Upload |
| an `inpsd.dat` with its referenced `posfile`, `momfile`, and exchange file; the |
| explicit cell in `inpsd.dat` is required for reciprocal-space calculations. |
|
|
| ## Documentation |
|
|
| - [Theory and scientific scope](docs/THEORY.md) — Hamiltonian, Fourier |
| convention, induced response, downfolding, magnons, and interpretation |
| limits. |
| - [Usage guide](docs/USAGE.md) — installation, input format, application |
| workflow, CLI, and Python examples. |
| - [Development and deployment guide](docs/dev/DEPLOYMENT.md) — local workflow, |
| release checks, and Hugging Face Spaces deployment. |
|
|
| ## Validation |
|
|
| Run the test suite from the repository root: |
|
|
| ```bash |
| PYTHONPATH=src pytest -q |
| ``` |
|
|
| The bundled tests cover input parsing, reciprocal-space conventions, |
| symmetry expansion, induced-response conditioning, variational downfolding, |
| and FM magnon behaviour. |
|
|
| ## References |
|
|
| - O. N. Mryasov *et al.*, “Temperature-dependent magnetic properties of |
| FePt: Effective spin Hamiltonian model,” *Europhysics Letters* **69**, 805 |
| (2005), [arXiv:physics/0411020](https://arxiv.org/abs/physics/0411020). |
| - S. Polesya *et al.*, “Finite-temperature magnetism of Fe$_x$Pd$_{1-x}$ and |
| Co$_x$Pt$_{1-x}$ alloys,” *Physical Review B* **82**, 214409 (2010), |
| [arXiv:1008.3784](https://arxiv.org/abs/1008.3784). |
|
|
