Jahn–Teller effect in the 4T2g excited state of Cr3+ ion in Cs2NaYF6 crystal

Calculations of the fine structure of Cr3+ energy levels in Cs2NaYF6 accompanied by estimations of the Jahn–Teller (JT) stabilization energy in the first excited 4T2g state of Cr3+ ion are presented. Two independent approaches—effective second-order spin–orbit Hamiltonian and analysis of the potential energy surfaces—are used. The JT energy was estimated to be 216 and 257 cm–1 in the first and the second models, respectively. It is shown that the octahedral [CrF6]3− complex undergoes an equatorial expansion by 0.09 Å and an axial elongation by 0.02 Å due to the combined effect of the a1g and eg normal modes.