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

• Published in: Physical review. B 2021-07, Vol.104 (1), p.1
• Main Authors: Pal, Srishti, Debnath, Koyendrila, Gupta, Satyendra Nath, Harnagea, Luminita, Muthu, D V S, Waghmare, Umesh V, Sood, A K
• Format: Article
• Language: English
• Subjects: Anomalies; Debye-Waller factor; Density functional theory; First principles; Phase transitions; Synchrotrons; Transition metal compounds; Transition pressure; X ray powder diffraction; X-ray diffraction
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.104.014108

We study pressure-induced structural evolution of vanadium diselenide ( VSe2 ), a 1T polymorphic member of the transition metal dichalcogenide (TMD) family, using synchrotron-based powder x-ray diffraction (XRD) and first-principles density functional theory (DFT). Our XRD results reveal anomalies at P ∼ 4 GPa in the c/a ratio, V-Se bond length, and Se-V-Se bond angle, signaling an isostructural transition. This transition is followed by a first-order structural transition from the 1T (space group P3m1) phase to a 3R (space group R3m ) phase at P ∼ 11 GPa due to sliding of adjacent Se-V-Se layers. Both the transitions at ∼ 4 and 11 GPa are cognate with associated changes in the Debye-Waller factors not reported so far. We present various scenarios to understand the experimental results within DFT and find that the 1 T to 3 R transition is captured using spin-polarized calculations with Hubbard correction ( Ueff = U − J = 8 eV ), giving a transition pressure of ∼ 9 GPa, close to the experimental value.