Forces in EDO-TTF: Theoretical study of isotope and charge effects on vibronic coupling

Isotope and charge effects on vibronic coupling constant (V) and energy gradient (g) of ethylenedioxy-tetrathiafulvalen (EDO-TTF) upon the electron injection into cation and electron removal from neutral molecule are investigated. It is found that normal modes which include C = C stretching motion generally have large V and g. For electron removal, three normal modes (v460, v470, and v480) have large Vi+ and gi+, and deuteration results in decrease of V46+ and increase of V47+. For electron injection, five normal modes (ν+42, ν+44, ν+45, ν+47, and ν+48) have large vi0 and gi0 deuteration results in increase of V045 and V048 and decrease of V047. From the analysis of vibronic coupling constants using vibronic coupling density (VCD), regional vibronic coupling constant (RVCC), and atomic vibronic coupling constant (AVCC), it is revealed that the change in normal mode vectors (d) due to the deuteration and electron removal (or injection) leads to the change in V.