Fan Xaiofeng, Singh David J, Jiang Q, Zheng W T
College of Materials Science and Engineering, Jilin University, Changchun 130012, China.
Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211-7010, USA.
Phys Chem Chem Phys. 2016 Apr 28;18(17):12080-5. doi: 10.1039/c6cp00715e.
Two-dimensional crystals with weak layer interactions, such as twisted graphene, have been a focus of research recently. As a representative example, transitional metal dichalcogenides show a lot of fascinating properties due to stacking orders and spin-orbit coupling. We analyzed the dynamic energy barrier of possible phase transitions in MoX2 (X = S, Se and Te) with first-principles methods. In the structural transition from 2Hc to 2Ha, the energy barrier is found to be increased following an increase of pressure which is different from the phase transition in usual semiconductors. Among MoS2, MoSe2 and MoTe2, the energy barrier of MoS2 is the lowest and the stability of both 2Hc and 2Ha is reversed under pressure for MoS2. It is found that the absence of a phase transition in MoSe2 and MoTe2 is due to the competition between van der Waals interaction of layers and the coulomb interaction of Mo and X in nearest-neighbor layer of Mo in both phases.
具有弱层间相互作用的二维晶体，如扭曲石墨烯，近来一直是研究热点。作为一个典型例子，过渡金属二卤化物由于其堆叠顺序和自旋轨道耦合展现出许多迷人的特性。我们用第一性原理方法分析了MoX2（X = S、Se和Te）中可能的相变的动态能垒。在从2Hc到2Ha的结构转变中，发现能垒随压力增加而升高，这与普通半导体中的相变情况不同。在MoS2、MoSe2和MoTe2中，MoS2的能垒最低，并且在压力下MoS2的2Hc和2Ha两者的稳定性发生了反转。研究发现，MoSe2和MoTe2中无相变是由于两个相中层间范德华相互作用与Mo及其最近邻层中X的库仑相互作用之间的竞争。
