Ultralow lattice thermal conductivity at room temperature in 2D KCuSe from first-principles calculations

Abstract

Ultralow lattice thermal conductivity is crucial to achieve a high thermoelectric figure of merit for thermoelectric applications. In this work, using the first-principles and phonon Boltzmann transport theory, we investigate...

A van der Waals p–n heterostructure of GaSe/SnS2: a high thermoelectric figure of merit and strong anisotropy

“…On the whole, the lattice thermal conductivity decreases with increasing temperature, following the general law of κ l ∝ 1/ T , indicating that the U-process dominates the three-phonon scattering. 52 At 300 K, the κ l values in the x - and y -directions are 14.61 and 15.43 W m −1 K −1 , respectively, which are much smaller than those of MoS 2 /WS 2 (68.44 W m −1 K −1 ) 53 and WSe 2 /SnS 2 vdWHs (22.69 W m −1 K −1 ). 22 It is intriguing that the κ l of GaSe/SnS 2 exhibits a weak anisotropy, which does not appear in its constituents.…”

“…Therefore, we only focus on these eight phonon branches (phonon frequencies around 0–4.74 THz). The lattice thermal conductivity can be expressed as 52 where V is the volume of the primitive cell, and C , τ and ν are the specific heat, phonon relaxation time and phonon group velocity, respectively. λ denotes each phonon mode, and α is the Cartesian direction.…”

Ultralow lattice thermal conductivity in bulk and monolayer TlCuSe: a comparative study from first-principles

“…The previous studies have indicated that the Coulomb interaction is important to guarantee the dynamical stability for some d or f electron systems such as TiS 2 and U 3 Si 2 [23,24], and thus the Coulomb interactions are considered by using the effective Hubbard U values of 7 eV and 4 eV for 5d electrons of Tl atom and 3d electrons of Cu atom, respectively, because the Tl 4f electrons are far below the Fermi level. These U values have been used in some systems including Tl and Cu atoms such as Tl 3 TaS 4 , UTl 3 , KCuSe and CuO [25][26][27][28]. The kpoint meshes of 12 × 12 × 6 and 12 × 12 × 1 are used for bulk and monolayer TlCuSe, respectively.…”