[ Identification | Description | Input parameters | Links ]
MCViNE_Phonon_CoherentInelastic_SingleXtal ComponentSingle-crystal coherent one-phonon scattering with dispersion and polarization vectors from MCViNE IDF files (periodic over the reciprocal cell b1,b2,b3 given in Qgridinfo; orient the crystal by rotating the component). For a final direction (4pi, or a cone towards a target when focus_r>0) and a random branch among those with Emin < 1.5 Ei, all final speeds solving omega(Q) = |Ei-Ef| are found (Ridders' method on nsteps sub-intervals of [0,2vi]); one is chosen and weighted by the delta-function Jacobian, |sum_d b_d/sqrt(M_d) exp(iQ.d)(Q.e_d)|^2, Bose and Debye-Waller factors. Transport (same as MCViNE HomogeneousNeutronScatterer): on the first passage the neutron is forced to scatter at a uniformly chosen depth, weighted by path length, attenuation exp(-(mu+sigma)x) and the scattering coefficient; on exit it is attenuated by exp(-(mu+sigma)L_out). With order>1 further scatterings are sampled analogically (truncated exponential). With p_transmit>0 that fraction of events is kept as the attenuated direct beam. mu(v) = absorption_coefficient*2200/v. Events for which the kernel cannot scatter (kinematically forbidden) are absorbed. Geometry: box (xwidth,yheight,zdepth), cylinder (radius,yheight), hollow cylinder (+thickness) or sphere (radius only). All vectors (Q, targets, reciprocal vectors, atom positions) are in the component's local frame. Uses the shared runtime share/mcvine-lib.h/.c. Example: MCViNE_Phonon_CoherentInelastic_SingleXtal(idf_dir="MCViNE/fcc_toy_phonons", atoms="MCViNE/fcc_toy_atoms.dat", T=300, xwidth=0.01, yheight=0.01, zdepth=0.01)
| 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 | |
| target_x | m | Target position (component frame) x | 0 | |
| target_y | m | Target position y | 0 | |
| target_z | m | Target position z | 0 | |
| target_index | 1 | Relative index of a component to aim at (overrides target_x/y/z when non-zero) | 0 | |
| focus_r | m | Radius of the target disk; 0: scatter into 4pi (MCViNE default) | 0 | |
| deltaV_Jacobi | 1 | Relative velocity step for the numerical Jacobian | 0.001 | |
| nsteps | 1 | Sub-intervals for the root search in vf | 100 | |
| xacc | m/s | Root accuracy in vf | 10 | |
| unbiased | 1 | 0: MCViNE sampling (retries up to 100 direction/branch draws until omega(Q)=|Ei-Ef| has a solution, without correcting the weight: over-estimates when many directions have no solution). 1: single attempt, unbiased | 0 | |
| radius | m | Outer radius of a cylinder (with yheight) or of a sphere (yheight=0) | 0 | |
| xwidth | m | Width of a box sample | 0 | |
| yheight | m | Height of a box or cylinder sample | 0 | |
| zdepth | m | Depth of a box sample | 0 | |
| thickness | m | Wall thickness of a hollow cylinder (0: filled) | 0 | |
| pack | 1 | Packing factor (scales absorption and scattering coefficients) | 1 | |
| p_transmit | 1 | Monte Carlo fraction of events kept as unscattered transmitted beam (0: always scatter) | 0 | |
| order | 1 | Maximum number of scattering events per neutron (1: single scattering) | 1 |
| AT ( | , | , | ) RELATIVE | |||
|---|---|---|---|---|---|---|
| ROTATED ( | , | , | ) RELATIVE |
MCViNE_Phonon_CoherentInelastic_SingleXtal.comp.
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