Structure and lattice distortions of orthorhombic crystals with 3d ions

Formation of the orthorhombic phase of perovskite crystals with 3d elements has been considered and models of the crystal structures of LaMnO3, LaTiO3, YTiO3, LaVO3, and YVO3 have been constructed. A generalization of the results of previous studies has been performed with allowance for the effect of T2g distortions. An analysis of local symmetrized distortions has shown that the structure of compounds with Ti3+ and V3+ ions is determined by the “rotational” distortions of the T1g type (Qx, Qy, Qz); the T2g distortions are only secondary. At the same time, in LaMnO3 of special importance are Jahn-Teller Eg distortions. All the crystals examined exhibit a strong coupling between the lattice and electronic degrees of freedom, which manifests itself in strong vibronic effects. In particular, the terms of the vibronic Hamiltonian that are quadratic in Qx, Qy, and Qz determine the orbital structure of t2g compounds.