EFFECT OF ELECTRON CORRELATION ON VIBRATIONAL FREQUENCIES OF A(G) MODES IN C-60

The effect of electron correlation on the vibrational frequencies of two Ag modes in C60 is studied by using the Gutzwiller ansatz to construct the correlated wave function. It is found that the electron correlation decreases the frequencies of the Ag modes if the electron-phonon coupling is weak, whereas the correlation increases these frequencies if the electron-phonon coupling is strong. For the realistic strength of the electron-phonon and electron-electron interactions in C60, the correlation results in an observable reduction of the frequencies of these modes. The physical reasons of these features are discussed. © 1995 The American Physical Society.