Geometric and Electronic Properties of Monolayer HfX2 (X = S, Se, or Te): A First-Principles Calculation
Thi My Duyen Huynh, Duy Khanh Nguyen, Thi Dieu Hien Nguyen, Vo Khuong Dien, Hai Duong Pham, Ming-Fa Lin
Abstract
The essential properties of monolayer HfX 2 (X = S, Se, or Te) are fully explored by first-principles calculations. The optimal lattice symmetries, sublattice buckling, electronic energy spectra, and density of states are systematically investigated. Monolayer HfS 2 , HfSe 2, and HfTe 2, respectively, belong to middle-gap semiconductor, narrow-gap one and semimetal, with various energy dispersions. Moreover, the van Hove singularities (vHs) mainly arise from the band-edge states, and their special structures in the density of states strongly depend on their two or three-dimensional structures and the critical points in the energy-wave-vector space. The above-mentioned theoretical predictions are attributed to the multi-orbital hybridizations of [ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="minf1"><mml:mrow><mml:msub><mml:mi>d</mml:mi><mml:mrow><mml:msup><mml:mi>x</mml:mi><mml:mn>2</mml:mn></mml:msup><mml:mo>−</mml:mo><mml:msup><mml:mi>y</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:mrow></mml:msub></mml:mrow></mml:math> , d xy , d yz , d zx , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="minf2"><mml:mrow><mml:msub><mml:mi>d</mml:mi><mml:mrow><mml:msup><mml:mi>z</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:mrow></mml:msub></mml:mrow></mml:math> ]–[s, p x , p y , p z ] in the Hf-X chemical bonds. The diversified physical phenomena clearly indicate a high potential for applications, as observed in MoS 2 -related emergent materials ions.