Pressure induced structural transitions, coordination crossover, and optoelectronic response in divalent metavanadate CaV2O6
Abstract
High-pressure synchrotron X-ray diffraction, Raman spectroscopy, photoluminescence (PL), and UV-Vis absorption measurements were carried out on the divalent metavanadate CaV2O6 up to 31 GPa at room temperature. Ambient CaV2O6 crystallizes in a centrosymmetric pseudo-brannerite monoclinic structure (C2/m), where vanadium atoms reside in fivefold-coordinated VO5 trigonal bipyramids. Under hydrostatic compression, the system undergoes a structural phase transition starting at ∼1 GPa to a lower-symmetry, non-centrosymmetric monoclinic phase (C2), which becomes the single stable phase above 5.2 GPa. This transition involves an increase in vanadium coordination from VO5 bipyramids to edge-sharing distorted VO6 octahedra. High-pressure Raman scattering corroborates the structural phase boundaries, exhibiting mode softening (γ3 = −0.42, γ9 = −0.46) within the mixed-phase regime (1.0 - 4.4 GPa) and sharp anomalies in mode frequencies and linewidths across 5.2 GPa. The optical measurements show complete PL quenching near 1 GPa due to non-radiative recombination pathways introduced by local polyhedral distortions, alongside a non-monotonic evolution of the indirect optical band gap. Above 20 GPa, an anomaly in polyhedral distortion and internal strain drives an isosymmetric structural modification within the C2 phase, marked by an alteration in bulk compressibility and stabilization of the optical gap. Comparative high-pressure band-gap measurements on the sister compound MgV2O6 validate the explicit coupling between cation coordination changes and optoelectronic response in divalent metavanadates.
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BibTeX
@misc{giri2026pressure,
title = {{Pressure induced structural transitions, coordination crossover, and optoelectronic response in divalent metavanadate CaV$_2$O$_6$}},
author = {Bhagyashri Giri and Asish Kumar Mishra and Bidisha Mukherjee and Debabrata Samanta and Nico Giordano and Goutam Dev Mukherjee},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.01290},
eprint = {2610.01290},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.01290},
}
RIS
TY - UNPB
TI - Pressure induced structural transitions, coordination crossover, and optoelectronic response in divalent metavanadate CaV_2O_6
AU - Bhagyashri Giri
AU - Asish Kumar Mishra
AU - Bidisha Mukherjee
AU - Debabrata Samanta
AU - Nico Giordano
AU - Goutam Dev Mukherjee
PY - 2026
DA - 2026/10/09
PB - arXiv
DO - 10.48550/arxiv.2610.01290
UR - https://arxiv.org/abs/2610.01290
AB - High-pressure synchrotron X-ray diffraction, Raman spectroscopy, photoluminescence (PL), and UV-Vis absorption measurements were carried out on the divalent metavanadate CaV_2O_6 up to 31 GPa at room temperature. Ambient CaV_2O_6 crystallizes in a centrosymmetric pseudo-brannerite monoclinic structure (C2/m), where vanadium atoms reside in fivefold-coordinated VO_5 trigonal bipyramids. Under hydrostatic compression, the system undergoes a structural phase transition starting at ∼1 GPa to a lower-symmetry, non-centrosymmetric monoclinic phase (C2), which becomes the single stable phase above 5.2 GPa. This transition involves an increase in vanadium coordination from VO_5 bipyramids to edge-sharing distorted VO_6 octahedra. High-pressure Raman scattering corroborates the structural phase boundaries, exhibiting mode softening (γ_3 = −0.42, γ_9 = −0.46) within the mixed-phase regime (1.0 - 4.4 GPa) and sharp anomalies in mode frequencies and linewidths across 5.2 GPa. The optical measurements show complete PL quenching near 1 GPa due to non-radiative recombination pathways introduced by local polyhedral distortions, alongside a non-monotonic evolution of the indirect optical band gap. Above 20 GPa, an anomaly in polyhedral distortion and internal strain drives an isosymmetric structural modification within the C2 phase, marked by an alteration in bulk compressibility and stabilization of the optical gap. Comparative high-pressure band-gap measurements on the sister compound MgV_2O_6 validate the explicit coupling between cation coordination changes and optoelectronic response in divalent metavanadates.
ER -