Pressure-induced 1T to 3R structural phase transition in metallic VSe2: X-ray diffraction and first-principles theory

Abstract

We study pressure-induced structural evolution of vanadium diselenide (VSe2), a 1T polymorphic member of the transition metal di-chalcogenide (TMD) family using synchrotron-based powder X-ray diffraction (PXRD) and first-principles density functional theory (DFT). Our XRD results reveal anomalies at P ~4 GPa in c/a ratio, V-Se bond length and Se-V-Se bond angle signalling an isostructural transition. This is followed by a first order structural transition from 1T (space group P-3m1) phase to a 3R (space group R-3m) phase at P ~11 GPa due to sliding of adjacent Se-V-Se layers. We present various scenarios to understand the experimental results within DFT and find that the 1T to 3R transition can be captured only after inclusion of enthalpic correction associated with errors in cell volume with underestimated transition pressure. The abrupt increase in the Debye-Waller factors of Se atoms by a factor of ~4 and hence the anharmonic effects across the structural transition pressure are hitherto not reported so far and hint a possible way to understand the mismatch between the experimental and theoretical transition pressure values.

18 pages, 5 figures, 1 table

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• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Pressure induced metallization with absence of structural transition in layered MoSe2
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Cited by in corpus (1)

• Atomic arrangement of van der Waals heterostructures using X-ray scattering and crystal truncation rod analysis