Geometric considerations of the monoclinic–rutile structural transition in VO2

Shian Guan (1) , Aline Rougier (1) , Matthew R. Suchomel (1) , Nicolas Penin (1) , Kadiali Bodiang (1) , Manuel Gaudon (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

The mechanism of the displacive phase transition in VO2 near the transition temperature is discussed in terms of a geometrical approach, combining simple calculations based on the Brown's band valence model and in situ X-ray diffraction experimental results. Considering that the structural origin is well linked to the electrostatic potential optimization as in a Peierls model, our geometrical calculations and experimental studies are in agreement and suggest that VO2 phase transition is the consequence of very short atomic shifts mainly associated to a decrease of the 2nd sphere coulombic interactions. Hence, at a given temperature, the allotropic form (monoclinic versus rutile form) offering the largest unit-cell volume is stabilized over the lower unit-cell volume allotropic, while the transition occurs at the intercept of the unit cell variation versus temperature of the two forms, which exhibit significantly different thermal expansion coefficients.

Domaines: Matériaux

Shian Guan, Aline Rougier, Matthew R. Suchomel, Nicolas Penin, Kadiali Bodiang, et al.. Geometric considerations of the monoclinic–rutile structural transition in VO2. Dalton Transactions, 2019, 48 (25), pp.9260-9265. ⟨10.1039/C9DT01241A⟩. ⟨hal-02319190⟩