VIBRATIONAL-MODES OF PHOTO-EXCITED IN QUASI-ONE-DIMENSIONAL HALOGEN-BRIDGED MIXED-VALENCE COMPOUNDS

Vibrational modes of photo-excited in quasi-one-dimensional halogen-bridged mixed-valence compounds are investigated by using tight-binding model for electrons and quasi-harmonic approximation for lattice vibration. Pt-halogen compound is taken as a one-dimensional two-atom base chain, and the unit cell contains 12 atoms and a 12 x 12 dynamical matrix D(ij) follows. Solving the corresponding determinantal equation numerically, the 12 eigenfrequencies are found. They are more accurate than the ones by harmonic approximation in comparison with the experimental data.