Theory of Pressure-Induced Hugh-Spin\(\)Low-Spin Transition in Compounds of Iron. II

The pressure-induced spin state transition in Fe(III) compounds are studied on the basis of the ligand field theory by using the model in which the couplings of Fe ion with a molecular distrotion and a lattice strain are taken into account. The calculated pressure dependences are classified into three patterns: (i) The continuous and discontinuous transitions from the high-spin state (HS) to the low-spin state (LS) with increasing pressure; (ii) the continuous and discontinuous transition from LS to HS; (iii) the multiple transition LS→HS→LS→HS . The discontinuous transitions are induced by the occurence or the disappearance of the cooperative intramolecular distortion.