Lily Anh wrote: > I am doing a high pressure study on CaO and I want to investigate the > bond property under compression. The Born effective tensor of cubic CaO > has only one independent component. The Born effective charge for Ca are > larger than the nominal ionic charge +2 and increase with pressure. Does > this mean the bond become more ionic or more covalent? Since the it > increase with pressure, can we say that more charge transfer from Ca to > O in this case?
effective charges are dynamical quantities, expressing the response to a perturbation, and should not be identified with ionicity, a static quantity expressing the amount of charge around an atom. More in the relevant literature Paolo -- Paolo Giannozzi, Democritos and University of Udine, Italy
