Development and verification of thermal neutron scattering law data calculation module in nuclear data processing code NECP-Atlas

A new module designed to generate thermal scattering law (TSL) data is developed in the nuclear data processing code NECP-Atlas, which is currently under development at Xi'an Jiaotong University. The module can calculate TSL data for solid materials of any crystal structure and liquid materials in the free gas or the Egelstaff and Schofield approximations. To acquire a precise description of the neutron thermalization, the module eliminates the cubic approximation and atom site approximation used in the conventional method. In addition, a technique based on the anisotropic displacement parameters method is implemented to consider the anisotropy of interatomic forces and the correlation of forces from different directions. Comparison with the LEAPR and the Debye–Waller matrix method used in ENDF/B-VIII.0 enabled verification of the TSL data generated by the module. The numerical results revealed the good performance of the module.