Two-dimensional transition metal chalcogenides with hexagonal and orthorhombic structures: candidates for auxetics and photocatalysts

Wenqi Xiong; Kaixiang Huang; Shengjun Yuan

paper

Two-dimensional transition metal chalcogenides with hexagonal and orthorhombic structures: candidates for auxetics and photocatalysts

arXiv:1905.07578

Abstract

In this paper, we perform theoretical study on the physical properties of two-dimensional transition metal chalcogenides MX $_{2}$ and M $_{2}$ X $_{3}$ (M= Ni, Pd; X= S, Se, Te). These studied materials are classified in three stable phases according to their lattice structures: hexagonal MX $_{2}$ , orthorhombic MX $_{2}$ and orthorhombic M $_{2}$ X $_{3}$ . They have either isotropic or anisotropic in-plane properties depending on their symmetries. In particular, the orthorhombic MX $_{2}$ and M $_{2}$ X $_{3}$ have low lattice symmetry and present highly anisotropic properties. The orthorhombic MX $_{2}$ possess giant negative in-plane Poisson's ratios, different from the other two phases. Moreover, by joint analysis of band gap, band edge and optical absorption, the orthorhombic MX $_{2}$ and M $_{2}$ X $_{3}$ are found to be highly efficient as water splitting photocatalysts within the visible and ultraviolet sunlight regions.