On Jan 10, 2012, at 8:22 , Ali Tavana wrote: > I am looking for the reference paper for the VCA implementation > in QE (i.e. virtual.x code).
there is no such paper. This is the VCA implementation in QE, if I remember correctly: V^{(vca)} = V_{loc)^{(vca)} + V_{nl}^{(vca)} where V_{loc)^{(vca)} = x V_{loc}^{(1)} + (1-x) V_{loc}^{(2)} and V_{nl)^{(vca)} = \sum_{ij} |\beta^{(1)}_i> x D^{(1)}_{ij} <\beta^ {(1)}_j| + \sum_{ij} |\beta^{(2)}_i> (1-x) D^{(2)}_{ij} <\beta^{(2)}_j| where V_{loc}^{(n)}(r) is the local part of PP n ; \beta^{{n)}_i(r) are the projectors for PP n ; D^{(n))_{ij} are the (bare) components of matrix D for PP n P. --- Paolo Giannozzi, Dept of Chemistry&Physics&Environment, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222