Anharmonicity in cubic boron arsenide: a machine-learning based force-field study

Due to a thermal conductivity that rivals diamond, cubic boron arsenide (c-BAs) has the potential to compete in the search for next-gen semi-conducting materials, where proper heat-management has become an increasingly important selection criterion. Based on experiments and theoretical predictions using the Boltzmann-transport equation (BTE) the high thermal conductivity is the result of a fortunate combination of effects: while c-BAs is in principle strongly anharmonic, as suggested by the temperature dependence of the thermal conductivity, the resulting three- and four-phonon scattering is suppressed effectively due to bunching of the acoustic modes and a large frequency gap between the acoustic and optical modes [1]. Alternatively, the lattice dynamics, vibrational properties and thermal conductivity can be obtained from molecular dynamics, since the required information is encoded in the trajectory of the atoms.

In this talk we are going to present our machine-learning based force-field calculations for the dynamics and thermal transport of c-BAs. The forcefield is based on the well-known lattice dynamics expansion of the total energy. With this particular choice we can obtain the higher-order force-constant tensors directly and gain further insight into the role of anharmonicity in c-BAs.

[1] L. Lindsay et al., Phys. Rev. Lett. 111, 025901 (2013)