Structural transition from marcasite to pyrite phase in FeSe 2 under high pressure: a first-principles study
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THE EUROPEAN PHYSICAL JOURNAL B
Regular Article
Structural transition from marcasite to pyrite phase in FeSe2 under high pressure: a first-principles study Mingsheng Yi, Jintao Wu, Xiaojun Zheng a , and Xing Ming b College of Science, Guilin University of Technology, Guilin 541004, P.R. China
Received 28 March 2020 / Received in final form 9 June 2020 / Accepted 14 August 2020 Published online 16 September 2020 c EDP Sciences / Societ`
a Italiana di Fisica / Springer-Verlag GmbH Germany, part of Springer Nature, 2020 Abstract. Based on density functional theory, first-principles simulations and calculations are carried out to study the structural stability and electronic properties of FeSe2 under high pressure. Present theoretical calculations not only reproduce successfully the lattice constants, bulk modulus, and indirect band gap of both the marcasite and pyrite phases at ambient conditions, but also predict a first-order phase transition from the marcasite to pyrite structure at 9 GPa under compression. Based on elastic constants and phonon spectra calculations and detailed analysis of the geometry structures, a possible mechanism of the structural transformation from marcasite to pyrite structure is presented. Furthermore, pressure-induced band gap enlargement is observed in the marcasite phase, which is benefit for the optical applications. By contrast, the band gap of the pyrite phase gradually decreases along with the compression, and finally closes up due to the broadening of bandwidths.
1 Introduction Along with the improvements of experimental instruments and research conditions, pressure, and stress become new degrees of freedom independent of temperature component to affect the structural and physicochemical properties of crystals [1–9]. The mechanical and transport properties of materials will change significantly under high pressure. Pressure-induced structural phase transition, superconductivity, and metal–insulator transition have been extensively reported in the transition metal dichalcogenides (TMDCs) materials MX2 (M and X represent transition metal and chalcogenide elements). For example, high pressure experiments and theoretical calculations reported that the orthorhombic layered PdSe2 material transformed into cubic pyrite structures under compression [1]. Recently, the cubic pyrite structure PdSe2 was reported to show superconducting properties under high pressure, and its superconducting temperature reached up to 13.1 K [2]. A pressure-induced new monoclinic layered PdSe2 was predicted by first-principles simulation, its single layer showing excellent visible-light optical absorption and high-mobility transport anisotropy [3]. At the same time, high-pressure-induced layeredorthorhombic to cubic-pyrite phase structural transitions and superconducting properties have also been observed in another TMDCs material PdS2 [4,5]. Furthermore, a b
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the superconductivity of 1T-TiTe2 exhibits very different behavior under hydrostatic and un
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