First-principles calculations of structural, electronic, optical, elastic properties and microscopic crystal field effects in Rb₂CrF ₆

In the present work we report on the results of ab initio calculations of the optimized crystal structure, band structure, density of states (DOS), optical and elastic properties of Rb₂CrF₆, followed by the microscopic analysis of the crystal field effects for the 3d states of Cr ⁴⁺ ions. For the sake of consistency, both the local density approximation (LDA) and generalized gradient approximation (GGA) implemented in the CASTEP module of Materials Studio were used. The pressure dependences of the structural, electronic and elastic properties were analyzed for elevated pressures from 0 to 5 GPa with a step of 1 GPa. In addition, the dependence of the Cr⁴⁺ 3d states' positions on pressure has been analyzed carefully. The analytical dependences of the crystal field strength 10Dq on both pressure and Cr-F distance were obtained. To the best of the authors' knowledge, there are no experimental data on the band structure, elastic constants and absorption spectrum function for this host, so the present work is the first theoretical study of this kind, and the theoretically obtained results could be suggestions for future experiments.