Dysurf: A program for simulating four-dimensional dynamical structure factor

A Fortran program that can be applied to simulate the four-dimensional dynamical structure factors (Dysurf) for inelastic neutron and inelastic X-ray scattering experiments is presented. With the underlying theoretical formalism, the detailed implementation of the program is described. Based on the second-order force constants from the first-principles method, the Dysurf code can well reproduce the measured spectroscopies of those scattering experiments. Four main applications of this code with the corresponding examples are introduced here, including the multi-dimensional dynamical structure factors, thermal diffuse scattering, line cut at specific points in the Brillouin zone and sample design. This program will be helpful in terms of designing and explaining related inelastic scattering experiments.