Publication No.60



L. M. Prócel, F. Tipán, A. Stashans.  Mott-Wannier excitons 
in the tetragonal BaTiO3 lattice - Int. J. Quant. Chem., 
2002, Vol. 91, p. 586.

Abstract:
Structural and electronic properties of excitons in the tetragonal 
BaTiO3 crystal is studied using a quantum-chemical method developed 
for crystals. Obtained defect structure corresponds to the so-called 
Mott-Wannier-type exciton having a considerable distance between the 
hole and electronic parts of the defect. Performed crystalline lattice 
relaxation shows displacements of atoms in rather extensive defective 
region of up to twelve atoms. However, the calculated magnitudes of 
atomic movements are not large, normally not exceeding 0.08 Å. It is 
also observed that the self-trapped exciton polarizes the lattice 
around it. Using the so-called delta (SCF) method, the luminescence 
energy due to the exciton is found to be equal to 0.94 eV. 




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