Embedded Peierls instabilityand the electronic structure of MoO2

Abstract

Molybdenum dioxide crystallizes in a monoclinic structure whichdeviates only slightly from the rutile structure and ischaracteristic of several early transition metal dioxides. Wepresent results of all-electron electronic structure calculations based on density functional theory within the local densityapproximation and using the augmented spherical wave method.The electronic properties of MoO2 are dominated by stronghybridization of O 2p and crystal-field-split Mo 4d stateswith bands near the Fermi energy originating almost exclusively fromMo 4d t2g orbitals. In additional calculations for ahypothetical high-symmetry rutile structure these bands separateinto quasi-one-dimensional d∥ states pointing along the rutile c-axis and the rather isotropically dispersing π* bands.On going to the monoclinic structure, the characteristic metal-metaldimerization causes strong splitting of the d∥ bandsinto bonding and antibonding branches which embrace the nearlyinert π* bands at EF. As a consequence,large portions of the Fermi surface are removed. According to ourcalculations the monoclinic structure of MoO2 thusresults from a Peierls-type instability of the d∥bands in the presence of, but still rather unaffected by, anembedding background of π* states. Our work has strongimplications for the current understanding of VO2 and thestriking metal-insulator/structural transition displayed by thismaterial.