Effects of low dimensionality on electronic structure and thermoelectric properties of bismuth

Abstract

First-principles calculations and Boltzmann transport theory have been combined to comparatively investigate the band structure, phonon spectrum, lattice thermal conductivity, and the transport properties of the β-bismuth monolayer and bulk Bi.

Phonon spectrum and thermoelectric properties of square/octagon structure of bismuth monolayer

“…One could also discern from Table 4 that for the s/o-bismuth monolayer, there is a sharp decrease of elastic constants compared with the Fig. 7 The phonon volumetric specific heat of s/o-bismuth and bbismuth monolayers 18 as the function of temperature. Table 3 The maximum frequency of the longitudinal acoustic branch (u m LA ), the maximum frequency of the transverse acoustic branch (u m TA ), the maximum frequency of the out-of-plane acoustic branch (u m ZA ), the maximum group velocity of the longitudinal acoustic branch (V m LA ), the maximum group velocity of the transverse acoustic branch (V m TA ), and the maximum group velocity of the out-of-plane acoustic branch (V m ZA ) of the s/o-bismuth and b-bismuth monolayer b-bismuth monolayer, and such a decrease in elastic constants would bring about weakened bond strength and subsequent low phonon velocity, which are consistent with the lower lattice thermal conductivity revealed in Section IIIB.…”

“…29,30 The effects of temperature and carrier density (n) are simulated using the rigid band approximation, [31][32][33] which assumes that the effects do not change the shape of the band structure, but only shi the Fermi energy. 18,34 The lattice thermal conductivity and phonon spectrum of the s/o-bismuth monolayer are calculated by using the Boltzmann transport equations for the phonons as implemented in ShengBTE code 35 and PHONOPY package. 36 To obtain the phonon spectrum and lattice thermal conductivity, the secondorder harmonic interatomic force constants (IFCs) are calculated using the density-functional perturbation theory (DFPT) with a 4 Â 4 Â 1 supercell.…”

“…14,15,17 In addition, one can also discern that the bond lengths (d 1 and d 2 ) and buckling parameter (DZ) of the s/obismuth monolayer is slightly less than that of the corresponding b-bismuth monolayer. 18 To gure out the impact of the electronic structure on the electric transport performance, the band structure and band gap of the s/o-bismuth monolayer are calculated and shown in Table 2 and Fig. 2.…”

“…Grüneisen parameters of s/o-bismuth and b-bismuth monolayers18 as the function of the frequency at the 300 K.…”

Effects of Bond Strength on the Electronic Structure and Thermoelectric Properties of β‐VA Monolayers (Sb, As, and P)

“…Specially, the β‐VA monolayers (Bi, Sb, As, and P) owing to the suitable intrinsic band gap and good stability, resulting in larger seebeck coefficient and power factor than MoS 2 , Graphene, Bi 2 O 2 Se, [7] makes it one of the most potential thermoelectric materials [8–10] . Therefore, the study for the β‐VA monolayer (P, As, Sb, and Bi) is mainly focused on regulating the phonon properties and electronic structure to improve the ZT value for high energy conversion efficiency by achieving high S and σ values and the low thermal conductivity during the past several years [8,11,12] . Unfortunately, the coupling of the above transport coefficients makes it challenging to significantly improve the overall thermoelectric performance.…”