Pressure-induced phase transition and electronic structure evolution in layered semimetal HfTe2

Abstract

Motivated by the recent experimental work, the pressure-induced structural transition of well-known two-dimensional (2D) 1T-HfTe2 was investigated up to 50 GPa through the advanced CALYPSO structure search technique combined with the first-principles calculations. Our calculations suggested that the 1T-HfTe2 will first transform to C2/m phase at 3.6 GPa with a volume reduction of 7.6% and then to phase at 9.6 GPa with a volume collapse of 4.6%. The occurrences of 3D C2/m and phases mainly originated from the enhanced Te–Te interlayer coupling and the drastic distortions of Hf–Te polyhedrons in phase under compression. Concomitantly, the coordination number of Hf atoms increased from six in to eight in C2/m and eventually to nine in at elevated pressure. The metallic and semimetallic nature of C2/m and phases were characterized, and the evidence of the reinforced covalent interactions of Te–Hf and Te–Te orbitals in these two novel high-pressure phases were manifested by the atom-projected electronic DOS and Bader charge.