[ Identification | Description | Input parameters | Links ]
MCViNE_Phonon_CoherentInelastic_PolyXtal_process ComponentPowder average of the coherent one-phonon cross section, computed from phonon energies and polarization vectors tabulated on a grid over one reciprocal cell (MCViNE IDF format, e.g. from phonopy via MCViNE tools). A random branch and a random Q vector in a cube are drawn until the event is kinematically allowed; phonon creation/annihilation, Bose factor and Debye-Waller factor included. Scattering coefficient: total coherent cross section / Vc. Union process. Part of the Union components: define this process, collect it into a material with Union_make_material (absorption is set there with my_absorption, the absorption inverse penetration depth at 2200 m/s), assign the material to Union_box/Union_cylinder/Union_sphere/Union_mesh geometries, and add a Union_master after them. Geometry, attenuation and multiple scattering are handled by Union_master; this component provides the MCViNE kernel: the scattering coefficient and the final-state sampling (weight). Isotropic process (powder/liquid-like); rotation is irrelevant. The kernel code is shared with the standalone component MCViNE_Phonon_CoherentInelastic_PolyXtal (mcvine-lib.c). Uses share/mcvine-lib.h/.c and share/mcvine-union-lib.h/.c; the process type MCViNE is declared in share/union-lib.h and registered with Union_master in share/mcvine-union-lib.h. Example: MCViNE_Phonon_CoherentInelastic_PolyXtal_process(idf_dir="MCViNE/fcc_toy_phonons", atoms="MCViNE/fcc_toy_atoms.dat", T=300, max_omega=45)
| Name | Unit | Description | Default | |
| idf_dir | str | Directory with MCViNE IDF phonon files: Qgridinfo, Omega2, Polarizations[, DOS] | 0 | |
| atoms | str | Atoms file: one row per atom 'x y z mass b_coh sigma_inc sigma_abs' ([AA] cartesian, [amu], [fm], [barn], [barn]), same order as in the IDF files | 0 | |
| T | K | Temperature | 300 | |
| dw_core | AA^2 | Debye-Waller core; <0: computed from the DOS (idf_dir/DOS or dos) | -1 | |
| dos | str | Optional DOS file for the Debye-Waller factor (default: idf_dir/DOS) | 0 | |
| Vc | AA^3 | Unit cell volume; 0: (2pi)^3/|b1.(b2 x b3)| from Qgridinfo | 0 | |
| max_omega | meV | Maximum phonon energy | 50 | |
| min_omega | meV | Phonons below this energy are skipped | 0.01 | |
| unbiased | 1 | 0: MCViNE sampling (rejection + empirical accessible reciprocal volume, a few % high in tests). 1: single Q sample in the cube with its exact volume, unbiased | 0 | |
| packing_factor | 1 | Packing factor (scales the scattering coefficient) | 1 | |
| interact_fraction | 1 | Union: fraction of interactions forced to this process (-1: by cross section) | -1 | |
| init | string | Deprecated and unused, accepted like on the other Union components (see Union_init). | "" |
| AT ( | , | , | ) RELATIVE | |||
|---|---|---|---|---|---|---|
| ROTATED ( | , | , | ) RELATIVE |
MCViNE_Phonon_CoherentInelastic_PolyXtal_process.comp.
[ Identification | Description | Examples | Input parameters | Links ]
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