Chemical bonding characterization, expansivity and compressibility of RECrO4

• The chemical bonding characterization of RECrO4 is presented.
• The thermal expansion coefficients and bulk moduli of RECrO4 are predicted.
• The predicted bulk moduli agree well with the experimental values.
• RE–O bonds contribute less to lattice energy.
• RE–O bonds contribute more to bulk modulus and thermal expansion coefficient.

Theoretical researches were performed on zircon-type RECrO4 (RE = rare earth elements) compounds by using dielectric chemical bond theory of complex crystals. The characterization of the chemical bonding, the expansivity and compressibility of the compounds were studied. The results revealed that both RE–O and Cr–O bonds were ionically dominated, and the ionicity fraction decreased gradually with the decreasing of the RE–O bond length. Cr–O bonds had a low linear thermal expansion coefficients (LTEC) and high bulk modulus than RE–O bonds. While the LTEC and bulk modulus of the compounds were mainly determined by RE–O bonds because they had a large bond volume. When RE varied from Pr to Lu, the LTEC decreased linearly from 6.00 to 5.71 10−6/K and the bulk modulus increased from 117.9 to 132.2 GPa. YCrO4 in zircon-phase had high lattice energy than YCrO4 in scheelite-phase, the bulk moduli of YCrO4 in zircon- and scheelite-phase were determined to be 135 GPa and 153 GPa, respectively, which agreed well with the experimental values.