Pressure-Induced Phase Transition and Band Gap Decrease in Semiconducting β-Cu₂V₂O₇

Abstract

The understanding of the interplay between crystal structure and electronic structure in semiconductor materials is of great importance due to their potential technological applications. Pressure is an ideal external control parameter to tune the crystal structures of semiconductor materials in order to investigate their emergent piezo-electrical and optical properties. Accordingly, we investigate here the high-pressure behavior of the semiconducting antiferromagnetic material β-Cu 2 V 2 O 7 , finding it undergoes a pressure-induced phase transition to γ-Cu 2 V 2 O 7 below 4000 atm. The pressure-induced structural and electronic evolutions are investigated by single-crystal X-ray diffraction, absorption spectroscopy and ab initio density functional theory calculations. β-Cu 2 V 2 O 7 has previously been suggested as a promising photocatalyst for water splitting. Now, these new results suggest that β-Cu 2 V 2 O 7 could also be of interest with regards to barocaloric effects, due to the low phase -transition pressure, in particular because it is a multiferroic material. Moreover, the phase transition involves an electronic band gap decrease of approximately 0.2 eV (from 1.93 to 1.75 eV) and a large structural volume collapse of approximately 7%.

Pressure-Induced Phase Transitions and Amorphization in HgCN(NO3)

“…The range of band-gap error values is 0.00–0.05 eV (Table S3, Supporting Information). Our results showing a large change of the band gap with pressure are consistent with a highly compressible material . The method used to determine the band-gap energy using Tauc plots tends to give an underestimated value .…”

“…Our results showing a large change of the band gap with pressure are consistent with a highly compressible material. 38 The method used to determine the band-gap energy using Tauc plots tends to give an underestimated value. 39 However, due to a lack of observation of any excitonic peak and even restricted plateau area at low pressures in the absorption spectra (due to instrument limitation), we could not use the Elliott−Toyozawa model for accurate band-gap determination.…”

An Investigation of the Pressure-Induced Structural Phase Transition of Nanocrystalline α-CuMoO4

“…The second fact that facilitates the reduction of volume in CuMoO 4 is that it can be achieved by tilting of the polyhedra. It should be noted that with respect to its polyhedral constitution, CuMoO 4 is more similar to Cu 3 V 2 O 8 and Cu 2 V 2 O 7 [45,46] than to typical orthomolybdates [47,48]. This is consistent in that the two vanadates have bulk moduli of 52 and 64 GPa, respectively; values that are comparable to the bulk modulus of αand γ-CuMoO 4 .…”

Computational high‐pressure chemistry: Ab initio simulations of atoms, molecules, and extended materials in the gigapascal regime

“…Due to this enormous pressure range, even planetary interiors can be modeled with a DAC. However, it should be noted that a pressure of less than 1 GPa can also induce effects like phase transitions and band gap alterations 20 …”