Investigation of the structural phase transition (SPT) on Cr3+ ion doped K2CdF4: A semi-empirical analysis

• A semi-empirical analysis of Cr3+ centers in K2CdF4 carried out.
• The structural phase transition (SPT) from 397 K to 301 K investigated.
• Local structural changes around Cr3+ center during SPT predicted.
• A deviation of the axial F-ligands from c-axis due to SPT demonstrated.

A semi-empirical analysis in the frame of superposition model (SPM) has been carried out to investigate the structural phase transition (SPT) on Cr3+ doped K2CdF4 host crystal. The change of the ZFSPs has been used for analyzing the crystal lattice distortions in the vicinity of the Cr3+ ion during SPT from tetragonal (TE) symmetry at 397 K to orthorhombic (OR) symmetry at 301 K. The phase change for this center has been investigated by means of three different structural models and various modeling approaches. We suggest that the structural differences for the Cr3+ center where the SPT occurs are caused by alternate rotation of CdF6 octahedra, similar to the SPT of cubic to TE in perovskite structure. The obtained results have been discussed in detail so as to predict the local structure and the exact position of the F− anions during the SPT in K2CdF4.