First-principles prediction of the lattice thermal conductivity of two-dimensional (2D) h-BX (X = P, As, Sb) considering the effects of fourth-order and all-order scattering.

Recently, cubic boron arsenide (c-BAs) has attracted global attention due to its higher lattice thermal conductivity (κ L), which is comparable to diamond, and excellent thermal properties. Can c-BAs achieve the leap in κ L after transforming its structure from three-dimensional (3D) to two-dimensional (2D) like diamond to graphene? Previous studies have only investigated the κ L considering three-phonon scattering and isotope scattering, and the calculated results are diverse. In this study, we first calculate second-order interatomic force constants (IFCs) and third-order IFCs to iteratively solve the Boltzmann transport equation (BTE) and to obtain the κ L 3 of monolayer hexagonal BX (X = P, As, Sb), h-BX (X = P, As, Sb), considering only three-phonon and isotope scattering. The corresponding κ L 3 of h-BX are 278.2, 205.7, and 20.2 W/mK at room temperature, and we explain the monotonous change that κ L 3 decreases with the increase of average atomic mass (mavg) different from previous studies. Subsequently we use regular residual analysis (RRA) to determine the necessity of including four-phonon scattering when calculating the κ L of monolayer h-BX. By calculating the fourth-order IFCs, we obtain the κ L 3 + 4 of monolayer h-BX including four-phonon scattering. The values of κ L 3 + 4 at room temperature are 61.12, 37.99, and 5.73 W/mK, which are highly consistent with the κ L ∞ of monolayer h-BX as predicted by the phonon spectral energy density (SED) method. The phonon SED method considers all-order scattering and gives values of 54.05 ± 21.48 W/mK (h-BP), 18.20 ± 4.47 W/mK (h-BAs), and 2.46 ± 0.34 W/mK (h-BSb), respectively. Our results show that the influence of four-phonon scattering on the κ L of monolayer h-BX is significant, and the κ L 3 + 4 and κ L ∞ still undergo monotonic changes after including four-phonon scattering. The main factors that determine the low (ultra-low) κ L of monolayer h-BAs (h-BSb) are large mavg and weaker bonding strength, the existence of intermediate frequency ZO and scattered acoustic branches, the strong anharmonicity caused by the in-plane vibrations of As (Sb) atoms, and four-phonon scattering. This study aims to end the variance within monolayer h-BAs κ L numerical simulation and demonstrate the potential of monolayer h-BSb in thermoelectric field applications. [ABSTRACT FROM AUTHOR]