The Berry phase is almost never present in it, with the exception of the "JT valley" caused by the Jahn-Teller effect, and it fails for graphenes, due to rigid oscillations of Dirac cones and a stiffening of the Raman G peak.  
The Berry phase is almost never present in it, with the exception of the "JT valley" caused by the Jahn-Teller effect, and it fails for graphenes, due to rigid oscillations of Dirac cones and a stiffening of the Raman G peak.  Its first step consists of solving the time-independent Schrodinger Equation to obtain namesake potential energy surfaces, which can be used to determine nuclear eigenvalues, while Eckart conditions are used in its second step.  The Franck-Condon principle assumes that the vibrational and electronic wavefunctions are separate in, FTP, this physical approximation used to model molecular dynamics, which assumes nuclei do not move in relation to electrons and is named for two physicists.
The Berry phase is almost never present in it, with the exception of the "JT valley" caused by the Jahn-Teller effect, and it fails for graphenes, due to rigid oscillations of Dirac cones and a stiffening of the Raman G peak.  
Born-Oppenheimer approximation