Thermal neutron scattering cross section of liquid FLiBe

The molten salt material Li2BeF4 (FLiBe) has been widely proposed as a moderator and coolant material in nuclear applications. Its usage and impact on neutron thermalization in the system requires accurate generation of FLiBe thermal neutron scattering libraries. In this work, liquid FLiBe is modeled using the classical molecular dynamics code LAMMPS. Experimental limits of liquid FLiBe properties are determined from reported databases. Predicted properties of FLiBe from molecular dynamics simulations including density, viscosity, and atomic species diffusivities are computed and compared to experimental data. To initiate the calculation of the thermal neutron scattering law, the velocity autocorrelation functions are calculated from molecular dynamics trajectories and subjected to Fourier transformation to obtain the density of states of possible excitations. Bound modes and diffusive modes of the density of states are separated to calculate the corresponding scattering law Sbound(α,β) and ,Sdiff(α,β) respectively. Thermal neutron scattering cross section libraries of F, Li, Be in FLiBe are generated at temperatures of 873 K, 923 K and 973 K in ENDF/B VII.1 format.