Not to be tedious, but let me raise this question again. First of all, k-point.f90 is a routine I've been writing for my own education, and in the bleariness of a late evening posting, I subliminally substituted it for kpoints.f. I did have a quick look at the latter code beforehand, but when I saw the phrase "special points," I took it to refer to the Bouckaert-Smolukowski-Wigner notation for high symmetry BZ "special points" I learned in my younger years (this is the sort of stuff you can find on the Bilbao website these days). I do see now the usage of the term in kpoints.f indeed means the calculation of an MP mesh. Thanks, Paolo.
What I was most concerned about was the generation of k-point meshes or nets for use as input to pw.x (nscf) for subsequent post-processing calculations, such as the computation of Fermi surfaces or optical properties. For example, the routine kvecs_FS.x appears to fill the reciprocal lattice of its input structure with uniformly spaced, equally weighted, point coordinates, whereas the method used to calculate the mesh used for the aluminum example of epsilon.x is unclear (at least to me). There is a warning in the documentation for epsilon.x that "reduction of the k-points grid into the irreducible BZ" is not supported. I also note that the conventional unit cell (ibrav = 1), not the Bravais or primitive fcc (ibrav = 2) coordinates are used in the example. Does this mean one can compute the mesh for epsilon.x using kvecs_FS.x and the "conventional" reciprocal cell coordinates? Finally, on the point of mesh visualization. I use XCrySDen a lot, especially for BZ and charge-potential visualizations. But I don't know how to configure or generate a .xsf file for a 3D mesh of discrete points. Paul M. Grant, PhD Principal, W2AGZ Technologies Visiting Scholar, Applied Physics, Stanford (2005-2008) EPRI Science Fellow (Retired) IBM Research Staff Member Emeritus w2agz at pacbell.net http://www.w2agz.com ? ? -----Original Message----- From: pw_forum-bounces at pwscf.org [mailto:[email protected]] On Behalf Of Paolo Giannozzi Sent: Monday, September 15, 2008 1:33 AM To: PWSCF Forum Subject: Re: [Pw_forum] k-point grids...and all that On Sep 15, 2008, at 5:30 , Paul M. Grant wrote: > The ability to compute weighted 1st BZ grids according to the > Monkhorst-Pack scheme is included somewhere within espresso-4.0, > but exactly where is unclear (k-points.f90? No). > of course no, since it is non-existent: $ ls -l */k-points.f90 ls: */k-points.f90: No such file or directory There is however an auxiliary code, pwtools/kpoints.f, that produces Monkhorst-Pack grids with weights (executable: kpoints.x). Inside q-e, there are several routines for the generation of automatic k-point grids. See PW/setup.f90, under ! ! ... Automatic generation of k-points (if required) ! Routines kpoint_grid_efield and kp_strings are specific for macroscopic field and Berry phase calculations; kpoint_grid and setupkpoint (undocumented) take care of the typical scf case. The difference between the two is just aesthetic. > Finally, is there a visualization tool to display the k-point > distribution within the 1st BZ? XcrysDen? > for sure: see http://www.xcrysden.org/img/xcrysden-in-action.png, first picture Paolo --- Paolo Giannozzi, Dept of Physics, University of Udine via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222 _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum
