Effect of local structure on electron paramagnetic resonance spectra for trigonal [Cr(H2O)6]3+coordination complex in the sulfate alums series: a ligand field theory study

A simple theoretical method is introduced for studying theinterrelation between electronic and molecular structures. Bydiagonalizing the $120times 120$ complete energy matrices, therelationships between zero-field splitting (ZFS) parameter $D$ andlocal distortion parameter $Delta theta $ for Cr$^{3 + }$ ionsdoped, separately, in $alpha$- and $beta$- alums are investigated.Our results indicate that there exists an approximately linearrelationship between $D$ and $Delta theta $ in a temperature range4.2--297~K and the signs of $D$ and $Delta theta $ are opposite toeach other. Moreover, in order to understand the contribution ofspin--orbit coupling coefficient $zeta $ to ZFS parameter $D$, therelation between $D$ and $zeta $ is also discussed.