[Pw_forum] Bond property analysis through Born effective charges calculation

[Paolo Giannozzi]

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