Thermal Conductivity of 3C/4H-SiC Nanowires by Molecular Dynamics Simulation

Abstract

Silicon carbide (SiC) is a promising material for thermoelectric power generation. The characterization of thermal transport properties is essential to understanding their applications in thermoelectric devices. The existence of stacking faults, which originate from the “wrong” stacking sequences of Si–C bilayers, is a general feature of SiC. However, the effects of stacking faults on the thermal properties of SiC are not well understood. In this study, we evaluated the accuracy of Tersoff, MEAM, and GW potentials in describing the thermal transport of SiC. Additionally, the thermal conductivity of 3C/4H-SiC nanowires was investigated using non-equilibrium molecular dynamics simulations (NEMD). Our results show that thermal conductivity exhibits an increase and then saturation as the total lengths of the 3C/4H-SiC nanowires vary from 23.9 nm to 95.6 nm, showing the size effect of molecular dynamics simulations of the thermal conductivity. There is a minimum thermal conductivity, as a function of uniform period length, of the 3C/4H-SiC nanowires. However, the thermal conductivities of nanowires weakly depend on the gradient period lengths and the ratio of 3C/4H. Additionally, the thermal conductivity of 3C/4H-SiC nanowires decreases continuously from compressive strain to tensile strain. The reduction in thermal conductivity suggests that 3C/4H-SiC nanowires have potential applications in advanced thermoelectric devices. Our study provides insights into the thermal transport properties of SiC nanowires and can guide the development of SiC-based thermoelectric materials.

Comparison and Assessment of Different Interatomic Potentials for Simulation of Silicon Carbide

“…However, SiC also contains 12% ionic bonds; thus, interatomic potentials like Tersoff are unable to accurately describe the optical branches, and the TA branch tends to be overestimated [ 19 ]. Previous research found that T90 potential can describe the acoustic branch of phonons well [ 35 ], but the acoustic branches obtained using Vashishta, EDIP, and MEAM potentials agree well with the DFT curves. Among them, the frequencies of the optical branches from Vashishta potential are in the same frequency range as those from DFT.…”

“…Overall, none of the interatomic potentials show imaginary frequencies when describing phonon dispersion curves. Some of the outcomes of interatomic potentials exhibit slight variations compared with previous research results [35], which are likely attributed to differences in the selected model sizes. To further investigate the accuracy of the dispersion curves, Table 7 summarizes the phonon frequencies at high-symmetry points for 3C-SiC.…”

“…Moreover, Vashishta potential shows agreement with experimental results, except for C 44 for 3C-SiC [ 27 ]. In the field of thermal properties, most studies have focused on the thermal conductivity of 3C-SiC [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ] and 4H-SiC [ 35 ]. The research revealed that compared with T89 potential, the thermal conductivity predictions by GW potential closely match the experimental results [ 32 ].…”

“…The research revealed that compared with T89 potential, the thermal conductivity predictions by GW potential closely match the experimental results [ 32 ]. In addition, studies using interatomic potentials to calculate phonon dispersion in SiC have focused on 3C-SiC [ 19 , 35 ]. The results indicate that Tersoff overestimates the optical branch of the dispersion curve [ 19 , 36 ], and compared with GW, MEAM, T05, and T89 potentials, T90 potential is better in describing phonon thermal transport [ 35 ].…”

“…In addition, studies using interatomic potentials to calculate phonon dispersion in SiC have focused on 3C-SiC [ 19 , 35 ]. The results indicate that Tersoff overestimates the optical branch of the dispersion curve [ 19 , 36 ], and compared with GW, MEAM, T05, and T89 potentials, T90 potential is better in describing phonon thermal transport [ 35 ]. However, there were only few comparisons of the prediction with these interatomic potentials on the elastic mechanics, thermal conductivity, and phonon dispersion curves for hexagonal SiC.…”