Sandro, I am replying to this old e-mail now because the funds have become available to do some work in this area.
I looked in Paolo Focher's thesis and there are some very helpful equations, so thank you. However, the eqn.'s are limited to LDA. Does anyone know where I could find the relevant equation(s) for the GGA functional contribution to the stress tensor? I imagine it should not be that different from LDA, but I want to be sure. On 7/13/06, Scandolo Sandro <scandolo at ictp.it> wrote: > > 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 > > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > -- Nichols A. Romero, Ph.D. 1613 Denise Dr. Apt. D Forest Hill, MD 21050 443-567-8328 (C) 410-306-0709 (O) -------------- next part -------------- An HTML attachment was scrubbed... URL: /pipermail/attachments/20070109/e3b74c62/attachment.htm
