Negative thermal expansion in isostructural cubic ReO3 and ScF3: A comparative study

Abstract

Negative thermal expansion (NTE) in isostructural cubic ReO3 and ScF3 were studied using first-principles calculations within the quasiharmonic approximation. The reproduced coefficients of NTE (CNTE) is in reasonable agreement with experiment and the NTE behavior was attributed to the vibrational modes which have the minimum negative values of Grüneisen parameters at M(0.5, 0.5, 0) and R(0.5, 0.5, 0.5) in Brillouin zone. The calculated CNTE of ReO3 is an order of magnitude smaller than that of ScF3 due to the stiffer covalent bonds in ReO3 as well as the vibrational modes which will generate a sharp energy-increasing antibonding state. Consequently, the NTE was suppressed in ReO3. Meanwhile, larger lattice constant and smaller bulk modulus than those of ReO3 also imply that ScF3 is expected to have larger coefficient of negative thermal expansion.