I have basically two questions to ask. I will like to mention that I have gone through the related previous questions and their answers on registered users site. I will be highly obliged if you could kindly spare some time to go through the following two queries.
1.) I was doing c/a optimization at five different volumes in bct structure for a particular case and was trying to get equilibrium volume and tentative value of bulk modulus and its pressure derivative. I gave optimization for one set of 5 volumes, say +5.0, 0.0, -5.0, -10.0, -15.0 and another set, say +5.5, 0.5, -5.5, -10.5, -15.5 and then get EOS, then I find that there is a huge difference in the value of pressure derivative of bulk modulus K? for the two cases. I have plotted both the cases together in the plot.ps file attached herewith. Here in the plot ?E? is the same constant value of energy for both the curves. Only thing is, for the sake of clarity of seeing the two curves together, in the solid curve 0.001 Ryd of energy is added so that it is shifted up by that much energy so that one can see the difference between the shape of two curves clearly. Both the curves as such don?t seem to be much different, then why such a large difference in K?. Even otherwise also, why should it matter whether the run is given for 1st set of volumes or the 2nd set of volumes. Could you please comment on this Prof. Blaha? 2.)While doing a spin-orbit calculation, we need to increase Emax upto 10 Ry in case.in1 file even though we are interested in eigenvalues near Fermi energy. But as said in users guide, in the "second-variation" these high eigenstates form the basis functions for the SO calculation. Without these high eigenvalues there will be a poor basis even for states near Fermi energy.. But these high eigenvalues are giving large QTL-B value of 980 or 1500 value, at high energies say around 4.0 in case.output2 file if emax is set as 5.0 (instead of the default value 1.5) in case.inso file also apart from a Emax=5 (default in SO calculations) in case.in1 file, when we try to calculate partial charges by giving the command 'x lapw2 -so -qtl'. After this, the command 'x tetra' is given to get density of states. So as said earlier, this is so when case.inso file also has emax = 5.0 i.e the maximum energy for which output eigenvectors and eigenenergies will be printed (p.96 of users guide). But if we put emax =1.5, which is the default value in case.inso file, then anyway at high energies no computation of eigenvectors and eigen energies is done and no such statement appears in the case.output2 file. It is true that fermi energy is far below the energy level at which high QTL-B is quoted in case.output2 file. My question here is: How and where Emax = 5.0 of case.in1 file is used so that getting large qtl-b in output2 while calculating partial charges, is meaningless or unharmful, if we happen to keep emax equal to 5.0 in case.inso also. I just want to confirm that a large qtl-b value at energies 0.5 to 1Ryd higher than Fermi energy in case.output2 file is harmless and that I can use Emax upto 10 in case.in1 file without any hesitation. I will highly appreciate your clarification on this. Thank you very much in advance for your attention and time. V. Mishra -------------- next part -------------- A non-text attachment was scrubbed... Name: plot.ps Type: application/postscript Size: 23196 bytes Desc: not available URL: <http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20120730/de0945ca/attachment.ps>