Dear Abinit users,

What is the unit of the ‘mode effective charge’ in the output of the anaddb postprocessing file? The mode effective charge tensor is a number_of_modes tensor x 3 tensor. In comparison, the Born effective charge tensor is a number_of_atoms x 3 x 3 tensor.

I am interested in the mode polarity tensor (also a number_of_modes x 3 tensor), which is defined as the matrix product between the Born effective charges and the eigendisplacements (see Eq 41 in https://journals.aps.org/prb/pdf/10.1103/PhysRevB.71.125107):

p_{m,\gamma} = \sum_{\kappa, \beta} Z_{\kappa, \gamma \beta} u_m(\kappa, \beta)

, and I would like to understand what is the mode effective charge tensor in relation to p_{m,\gamma} .

Moreover, in the future, where can I easily find the units of the outputs and variables in Abinit?

Many thanks,

Virginie de Mestral

PhD student at ETHZ