Structural, lattice dynamics and thermodynamic properties of Sr2VO4 from first principles

- More reasonable phonon mode assignments are got combining with experimental data.
- The anomalous peak of specific heat is confirmed from theoretical perspective.
- One reason of difficult to synthesize bulk single crystal is found from theory.

The structural, lattice dynamics and thermodynamic properties of Sr2VO4 are systematically explored from ab initio density functional theory. In order to describe correlated phenomena among the localized V 3d electrons, DFT + U method have been used. The Born effective charges, and vibrational properties are calculated based on lattice dynamics theory. The calculated phonon wave numbers of infrared normal mode are found to be in consistency with experimental values available present. By comparing with the experimental data, we get more reasonable mode assignments. Additionally, some thermodynamic properties, e.g., Helmholtz free energy, entropy, and heat capacity, are also analyzed based on quasi-harmonic approximation. Comparison of the calculated specific heat at constant pressure P = 0 GPa with previous experimental data can further confirm the anomalous peak around 100 K due to the orbital ordering transition. The rapid increase of thermal expansion coefficient around the crystal growth temperature, 1000-1300 K, may be one reason of resulting in the difficulty of synthesizing the bulk single crystal phase.