<div dir="ltr"><div><div><div><div><div><div><div><div>Hi Martin, <br><br></div>Thanks a lot for your help. I wanted to get back to you with either "yes it works" or "no it does not" but the truth is .. I'm not sure.<br><br></div>So I set EPS_SCF to 100 (1 was actually too small to have it "converge" within one step) and set ALPHA parameter to something very small (I tried 0 but, while parsing the input file ok, it's unhappy when calling a subroutine where it has to do something%ALPHA - fair enough). And I froze my QM atoms (I had forgotten that in the input file I attached last time). <br><br></div>It runs and terminates normally. Now I wanted to do few sanity check to make sure nothing too weird happens. Then I realize that it's actually quite difficult to find something to track in a QM/MM calculation to check that the density stays the same. I mean all energies will depend one way or another on the MM region so ... In the end I printed out the electron density and I'm not so happy with what it gives: <br><br></div>- I have a .wfn file (let's call it file1.wfn) from which I start a 100 step NVE MD at the QM/MM level (Run 1). Frozen QM atoms and mixing density with alpha = 10^-20. <br> &SCF<br> SCF_GUESS RESTART<br> MAX_SCF 10<br> EPS_SCF 100<br> EPS_DIIS 100<br> &MIXING<br> ALPHA 1e-20<br> &END MIXING<br> &END SCF<br><br>I print a new restart file, file2.wfn for this run. I print out the electron density cube files for each step<br></div>- I start a new 100step QM/MM (Run 2) from file2.wfn for which I also print out the electron density cube files. <br><br></div>I'm not so sure about that but I guessed that the .wfn file was being translated into the electron density. So I expected the last electron density of Run 1 to be identical to the first electron density of Run 2 (through file2.wfn). But that is not the case. This is a different issue I suppose but I'd like to be confident on the restart scheme too<br><br></div>The the first electron density cube file differs from the last electron density cube file for each run. Which surprises me with a machine-zero value for the coefficient. I'm thinking that if it generates deviations after 100 steps, what would happen after millions ... Then I tried alpha=10^-30 and there, all electron density cube files are empty. Which is even more surprising. I thought the mixing scheme was density = alpha*new density + (1- alpha)* old density. But that's not consistent with these results ...<br><br></div>puzzling!<br><div> <br><div><div><div><div><br> <br><div><br><br></div></div></div></div></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On 26 March 2015 at 07:51, M. Brehm <span dir="ltr"><<a href="mailto:brehmin...@googlemail.com" target="_blank">brehmin...@googlemail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi,<br><br>when I was just reading your question, I was thinking about a dirty hack which could do what you want:<br><br>Set EPS_SCF to something very large (e.g., 1), such that the SCF cycle will always converge after the first step. Then, turn on classical mixing, and set the ALPHA parameter to 0. This means that a new wave function is computed, but only "0%" of it are mixed into the old one, i.e., the initial wave function should remain constant.<br><br>Maybe this works :-)<br><br>Best regards,<br>Martin<br></div><div class="HOEnZb"><div class="h5">
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