A number of useful formulae can be found in Paolo Focher's thesis (1994) (dowloadable from http://www.sissa.it/cm/phd.php ), as well as in a subsequent publication:
Paolo Focher and Guido L. Chiarotti Ab-initio Molecular Dynamics simulations of structural phase transitions in ``Progress in Computational Physics of Matter'', eds. L. Reatto and F. Manghi, p. 1-42, World Scientific, Singapore, (1995). (I can fax you the relevant pages of the latter when I'm back to Trieste, late August). Best regards, Sandro > Hi, > > I and another post-doc are working on implementing a non-local > functional into PWSCF. It is of the general form: > E_xc[n(r)] = \int dr dr' n(r) phi(r,r') n(r') > > where n(r) and phi(r,r') are the charge density and a kernel, > respectively. > > Forces require calculating V_xc which is analytically complicated, but > has already been done. The next quantity that we want to compute is > the stress tensor. > > Does any happen to have any notes on calculating the stress tensor in > a PW basis set? > > I looked at the original paper on calculating the stress: > > O. H. Nielsen and R. M. Martin, Phys. Rev. Lett. 50, 697 (1983). > > Eqn. 3 contains the V_xc (mu_xc in their notation) and it also > contains epsilon_xc which is the exchange-correlation energy per > particle which cannot be easily written down in a closed analytic form > for a non-local functional (I think). Otherwise, I don't see any > higher derivatives of E_xc in the the expression for the stress. > > Does anyone have any useful references? > > Thanks, > -- > Nichols A. Romero, Ph.D. > 1613 Denise Dr. Apt. D > Forest Hill, MD 21050 > 443-567-8328 (C) > 410-306-0709 (O) > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >
