Tang Shuwei, Wan Da, Bai Shulin, Fu Shengkai, Wang Xinyu, Li Xiaodong, Zhang Jingyi
College of Materials Science and Engineering, Liaoning Technical University, Zhonghua Road. #47, Fuxin, Liaoning, 123000, China.
Faculty of Chemistry, Northeast Normal University, Changchun, Jilin, 130024, China.
Phys Chem Chem Phys. 2023 Aug 23;25(33):22401-22414. doi: 10.1039/d3cp03420h.
Inspired by the groundbreaking discovery of the 2H-MoS monolayer with outstanding physical properties, the electronic structure, structural stability, and thermal transport of 2H-CrX (X = S and Se) monolayers are theoretically evaluated using density functional theory (DFT) calculations and semiempirical Boltzmann transport theory. The 2H-CrX (X = S and Se) monolayers are direct semiconductors with the bandgaps of 0.91 and 0.69 eV. The elastic modulus and phonon dispersion curve analysis show that the 2H-CrX (X = S and Se) monolayers possess excellent mechanical and dynamic stabilities on account of elastic constants satisfying the Born-Huang criterion and the absence of negative frequencies. The thermal stabilities of the 2H-CrX (X = S and Se) monolayers at 300 K are proved by molecular dynamics (AIMD) simulations, as evidenced by the slight changes in the structural evolution and small fluctuation in total energy. High thermal conductivities of 131.7 and 88.6 W m K are discovered for 2H-CrS and 2H-CrSe monolayers at 300 K. Further analysis of the phonon group velocity, phonon relaxation time, and Grüneisen parameter shows that the high lattice thermal conductivities of 2H-CrX (X = S and Se) monolayers could be attributed to the great bond strength, large Young's modulus, relatively small atomic mass, high phonon group velocity, and long phonon relaxation time. In addition, the various scattering mechanisms are further considered in the calculations of phonon thermal transport to evaluate the effect of the scattering rates of the 2H-CrS and 2H-CrSe monolayers on the lattice thermal conductivity, and the determinative role is found for the phonon boundary scattering. Our present study would not only offer a fundamental understanding of the thermal transport properties of the 2H-CrX (X = S and Se) monolayers, but also provide theoretical guidelines for the experimental investigation of thermal management materials with 2H-phase.
受具有出色物理性质的2H-MoS单层的开创性发现启发，使用密度泛函理论（DFT）计算和半经验玻尔兹曼输运理论从理论上评估了2H-CrX（X = S和Se）单层的电子结构、结构稳定性和热输运。2H-CrX（X = S和Se）单层是直接半导体，带隙分别为0.91和0.69 eV。弹性模量和声子色散曲线分析表明，由于弹性常数满足Born-Huang准则且不存在负频率，2H-CrX（X = S和Se）单层具有出色的机械和动态稳定性。分子动力学（AIMD）模拟证明了2H-CrX（X = S和Se）单层在300 K时的热稳定性，结构演化的微小变化和总能量的小波动证明了这一点。在300 K时，发现2H-CrS和2H-CrSe单层的热导率分别为131.7和88.6 W m K。对声子群速度、声子弛豫时间和格林艾森参数的进一步分析表明，2H-CrX（X = S和Se）单层的高晶格热导率可归因于强键强度、大杨氏模量、相对较小的原子质量、高声子群速度和长声子弛豫时间。此外，在声子热输运计算中进一步考虑了各种散射机制，以评估2H-CrS和2H-CrSe单层的散射率对晶格热导率的影响，并发现声子边界散射起决定性作用。我们目前的研究不仅将提供对2H-CrX（X = S和Se）单层热输运性质的基本理解，还将为2H相热管理材料的实验研究提供理论指导。
