Vanadium <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>3</mml:mn><mml:mi>d</mml:mi></mml:math> charge and orbital states in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi mathvariant="normal">V</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mi>OPO</mml:mi></mml:mrow><mml:mn>4</mml:mn></mml:msub></mml:math> probed by x-ray absorption spectroscopy

V $3d$ charge and orbital states in ${\mathrm{V}}_{2}{\mathrm{OPO}}_{4}$ have been investigated by means of x-ray absorption spectroscopy (XAS). The electronic structure of ${\mathrm{V}}_{2}{\mathrm{OPO}}_{4}$ is very unique in that the charge transfer between ${\mathrm{V}}^{2+}$ and ${\mathrm{V}}^{3+}$ in face-sharing ${\mathrm{VO}}_{6}$ chains provides negative thermal expansion as reported by E. Pachoud et al. [J. Am. Chem. Soc. 140, 636 (2018)]. The near-edge region of O $1s$ XAS exhibits the three features which can be assigned to transitions to O $2p$ mixed into the unoccupied V $3d\phantom{\rule{4pt}{0ex}}{t}_{2g}$ and ${e}_{g}$ orbitals of ${\mathrm{V}}^{2+}$ and ${\mathrm{V}}^{3+}$. The V $2p$ XAS line shape can be reproduced by multiplet calculations for a mixed-valence state with ${\mathrm{V}}^{2+}$ and ${\mathrm{V}}^{3+}$. The polarization dependence of the O $1s$ and V $2p$ XAS spectra indicates V $3d$ orbital order in which $xy$ and $yz$ (or $zx$) orbitals are occupied at the ${\mathrm{V}}^{3+}$ site in the face-sharing chains. The occupied $xy$ orbital is essential for the antiferromagnetic coupling between the ${\mathrm{V}}^{2+}$ and ${\mathrm{V}}^{3+}$ sites along the chains, while the occupied $yz$ (or $zx$) orbital provides the antiferromagnetic coupling between the ${\mathrm{V}}^{2+}$ and ${\mathrm{V}}^{3+}$ sites between the chains.

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.