Dear, QE users I have been struggling for a while to find out what's going on with q2r.x The problem was that I could not get rid of the error messages below when doing q2r.x.
------------------------------------------------- DCFT3 : 2538-2030 The transform length (ARG NO. 9) is not an allowed value. The next higher allowed value is (2). ------------------------------------------------- I've compiled QE-v5.0.1. on AIX6.1(parallel machine) with 'mpxlf' with ESSL routines. So the 'q2r.x' calls 'cfft3d' and then the 'cfft3d' calls 'dcft3' in ESSL when performing FFT. The problem is this. The 'dcft3' in ESSL only accepts certain values of transforming length as shown in, ------------------------------------------------- http://publib.boulder.ibm.com/infocenter/clresctr/vxrx/index.jsp?topic=%2Fco m.ibm.cluster.essl.v5r1.essl100.doc%2Fam501_hscft3.htm ------------------------------------------------- so the FFT dimensions (nx, ny, nz), which is read from outputs by ph.x, should be the values in the table. Otherwise, the 'dcft3' crashes. The FFT dimensions (nx, ny, nz) in q2r.x are equivalent to the (nq1, nq2, nq3) in ph.x so that the Monkhorst-pack grid for ph.x should be limited by the values in the table when using the ESSL. For example, the Monkhorst-pack grid (16x16x1) for q-points in the case of two-dimensional supercell, such as graphene, cannot be accepted by the 'dcft3' so we have to avoid using the nq3=1. (For some reason, the 'dcft3' does not allow odd number of FFT dimensions..) So here is a question. I wonder if I can use the different Monkhorst-pack grid for pw.x and ph.x when calculating a phonon dispersion. For example, can I use the (16x16x1) k-points for pw.x and (16x16x2) q-points for ph.x. in the case of graphene or some two dimensional supercell ? I guess it should not be matter but I just want to be sure .. Thank you. Sincerely, JISEOK KIM, Ph.D. Postdoctoral Research Associate Department of Materials Science and Engineering University of Texas at Dallas 800 W. Campbell Rd. RL10 Richardson, TX 75080 (413)386-6285 -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120831/9bf23f85/attachment.htm