<DIV>Dear Marks,</DIV> <DIV> </DIV> <DIV>Thanks for your reply. you gave nice explanation. I will apply in my system to solve the problem. </DIV> <DIV> </DIV> <DIV>Regards,</DIV> <DIV>Santhy jaiker<BR><B><I>Laurence Marks <L-marks@northwestern.edu></I></B> wrote:</DIV> <BLOCKQUOTE class=replbq style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid">Let me try and explain a little. In general you want to have the RMT's<BR>as large as possible because then the calculations converge faster and<BR>also this is a better model for the core electrons. The RMT's that you<BR>need to have don't track with classic atomic radii but more what is<BR>going on with the core electrons, for instance for transition metals<BR>you generally want to have a larger RMT than for oxygen. What RMT you<BR>use also depends upon which states you decide to treat as semi-core,<BR>i.e. where you set the cutoff between core and valence in
lstart (and<BR>case.inc, case.in1, case.in2).<BR><BR>The Wien code cannot do a calculation if RMT's overlap. During<BR>minimization, often atoms will move quite close to each other, for<BR>instance if one wants to move to a very different position relative to<BR>the first. In this case you need to have a much smaller RMT than you<BR>would use for the optimized atomic positions.<BR><BR>The command "setrmt" will do this approximately for you. It is only a<BR>computer code, so you should look at what it is recommending, think<BR>about the values and run some tests (e.g. a simpler bulk structure) to<BR>understand what different RMT's mean. You should also look at the<BR>value of :NEC in case.scf and also the core integrals in case.outputm<BR>to check that you have adequately constrained the core electrons<BR>within the muffin-tins. No computer code is foolproof, the user has to<BR>make sensible decisions.<BR><BR>When you are running a minimization, you want to set things up
with<BR>your "best guess" as to how close the atoms are going to come during<BR>the minimization. If you think your starting point is very close to<BR>the minimized positions, you can use a small reduction; if you think<BR>you are far you may want to use a larger one. If you err with too much<BR>reduction this is not too large a problem; if you use too little the<BR>minimization won't run properly and you will have to adjust the RMT's<BR>(see the clminter command).<BR><BR>The standard way I run a minimization is to make a guess at the<BR>reduction, make the RMT's a bit smaller than this, use a smaller RKMAX<BR>(e.g. RKMAX/min(RMT)=2.5 to 3) and a smaller oversampling in case.in0,<BR>less k-points and less stringent convergence parameters (e.g. -fc 4<BR>not -fc 1). Only when the forces have reduced down to some reasonable<BR>level (e.g. 6-10 mRyd/au) do I change to more accurate values.<BR><BR>The value of "2" in nn is not particularly important, it is just how<BR>far out
the code prints out neighbors.<BR><BR>On Wed, Jul 2, 2008 at 6:21 AM, Santhy Jaiker <K_SANTHY79@YAHOO.CO.IN>wrote:<BR>> Dear wien2k users,<BR>> i have some basic doubts in % reduction of RMT. Any suggestion will be<BR>> appreciated.<BR>> · What is role of 'RMTreduction' in mini?<BR>> · What are the factors decides the %reduction of RMT?<BR>> · what is the minimum and maximum % reduction of RMT?<BR>> · nn distance i.e distance factor is usually 2. Is it applicable to<BR>> all the cases?<BR>> Thank is advance<BR>><BR>> Regards,<BR>> Santhy jaiker<BR>><BR>> Regards,<BR>> Santhy Jaiker<BR>><BR>> Research Scholar,<BR>> Materials Thermodynamics Lab,<BR>> Department of Metallurgical and Materials Engineering,<BR>> Indian Institute of Technology Madras,<BR>> Chennai - 600 036, India<BR>> Tel: 91-044-22575763<BR>> **********************************************<BR>> A truly happy person is one<BR>> who
can enjoy the scenery on a detour<BR>> **********************************************<BR>><BR>> ________________________________<BR>> Bring your gang together. Do your thing. Find your favourite Yahoo! Group.<BR>> _______________________________________________<BR>> Wien mailing list<BR>> Wien@zeus.theochem.tuwien.ac.at<BR>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien<BR>><BR>><BR><BR><BR><BR>-- <BR>Laurence Marks<BR>Department of Materials Science and Engineering<BR>MSE Rm 2036 Cook Hall<BR>2220 N Campus Drive<BR>Northwestern University<BR>Evanston, IL 60208, USA<BR>Tel: (847) 491-3996 Fax: (847) 491-7820<BR>email: L-marks at northwestern dot edu<BR>Web: www.numis.northwestern.edu<BR>Commission on Electron Diffraction of IUCR<BR>www.numis.northwestern.edu/IUCR_CED<BR>_______________________________________________<BR>Wien mailing
list<BR>Wien@zeus.theochem.tuwien.ac.at<BR>http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien<BR></BLOCKQUOTE><BR><BR><BR><DIV>Regards,</DIV> <DIV>Santhy Jaiker</DIV> <DIV> </DIV> <DIV>Research Scholar</DIV> <DIV>Materials Thermodynamics Lab</DIV> <DIV>Department of Metallurgical and Materials Engineering</DIV> <DIV>Indian Institute of Technology Madras</DIV> <DIV>Chennai - 600 036</DIV> <DIV>India</DIV> <DIV>Tel: 91-044-22575763<BR style="COLOR: rgb(191,95,0)"><SPAN style="COLOR: rgb(185,185,185)">**********************************************</SPAN><BR style="COLOR: rgb(185,185,185)"><SPAN style="COLOR: rgb(185,185,185)">A truly happy person is one</SPAN><BR style="COLOR: rgb(185,185,185)"><SPAN style="COLOR: rgb(185,185,185)">who can enjoy the scenery on a detour</SPAN><BR style="COLOR: rgb(185,185,185)"><SPAN style="COLOR: rgb(185,185,185)">**********************************************</SPAN><BR></DIV><p> 
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