We have developed a MATLAB code to calculate electron/hole hopping reorganization energies of molecules from their force constant matrices and optimized geometries in Cartesian coordinates in Gaussian output files. The reorganization energy can be calculated as the sum of vibrational potential energies, in harmonic oscillator approximation, corresponding to displacements along normal mode vectors. In order to extract vibrational modes and angular frequencies of a molecule, we first solved eigenvalue problem of its mass-weighted force constant matrix. We then translated atoms’ position for its center of mass to be the origin and aligned its molecule-body axes to its principal axes. Under the assumption that its principal axes are kept fixed before and after charge transfer, we calculated the displacements of neutral and charged states along their normal mode vectors. Optimized geometries and force constant matrices of neutral and charged states were calculated with Gaussian 03W and Gaussian 16W packages, where DFT-B3LYP method and 6-31G(d,p) basis were used.
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