The thermal transport and scattering channel of body centered cubic carbon BC14 using self-consistent phonon theory

Abstract

Using the self-consistent phonon (SCP) theory, lattice thermal expansion, and Boltzmann transport equation (BTE), both thermal conductivity and scattering channel are studied by considering the cubic and quartic anharmonicity. The increase of phonon group velocity is caused by phonon frequency shifts at about 12 THz, but the phonon group velocity decreases slightly above 15 THz, agreeing with the decrease of phonon frequency induced by quartic anharmonic renormalization. The relaxation time of SCP is larger than that of HA, leading to the increase of thermal conductivity under SCP. The glass-like thermal conductivity of HA+ 3 ph, HA+ 3 ph + 4 ph, SCP+ 3 ph and SCP+ 3 ph + 4 ph is 0.12517 W/mK, 0.15713 W/mK, 0.1187 W/mK, 0.28551 W/mK, respectively. The three-phonon weighted phase space of HA is slightly larger than that of SCP, while the four-phonon weighted phase space of HA is nearly the same as the phase space of SCP. The major contributions to the scattering channels are X + ZA/TA/LA→O, X→O+ZA/TA/LA, X + O+ZA/TA→O, X + O-O/TA/LA→O, X + O-O→ZA/TA/LA, and X-O-ZA/TA→O. The weak C-C bonding is responsible for the low thermal conductivity of BC14. Moreover, these findings help us to understand the physical mechanism of thermal transport with the effect of quartic anharmonic renormalization.