<DIV id=RTEContent> <DIV id=RTEContent>Dear Wien2k users,</DIV> <DIV> </DIV> <DIV>First, please forgive me if my questions are old and boring. </DIV> <DIV>I am new to the electronic structure business so I get </DIV> <DIV>bothered easily when things are not going right.</DIV> <DIV> </DIV> <DIV>I tried to compute the cohesive energy of silicon and Nitrogen, </DIV> <DIV>following the description outline in the Wien2k FAQ. The </DIV> <DIV>problem is that I get too many warnings . There is a warning attached to the </DIV> <DIV>total energy and a warning that indicates that RKmax has </DIV> <DIV>been reduced to NMATMAX. </DIV> <DIV> </DIV> <DIV>I have read previous emails along this line but still don't get a </DIV> <DIV>clear answer. I clearly understand that the Rkmax warning is due </DIV> <DIV>the value to which NMATMAX in the source. But I have tried reducing the Rkmax </DIV> <DIV>and RMT and I still get the warnings. Even though the scf i!
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converge, </DIV> <DIV>the warning signs give me cause to to doubt (though previous emails tend to suggest </DIV> <DIV>that it should not really matter) </DIV> <DIV> </DIV> <DIV>My questions are:</DIV> <DIV> </DIV> <DIV>(1) For small atoms like Nitrogen and Silicon, what are the reasonable values of RMT </DIV> <DIV>and Rkmax should be chosen without getting warnings.</DIV> <DIV> </DIV> <DIV>(2) Say I perform the computation with a 30 Bohr FCC lattice and I get a </DIV> <DIV>converged energy (hopefully without any warnings). How do I know for </DIV> <DIV>sure that the result that I'm getting is reliable. Should I increase the lattice </DIV> <DIV>constant, recomputed the energy and see the margin of error. If so, by how much do</DIV> <DIV> I increase the lattice constant, and for approximately how many lattice constants. In short, I want makes sure that I getting the right energies. </DIV>
<DIV> </DIV> <DIV>Thanks a million!</DIV> <DIV> </DIV> <DIV>John Appleton</DIV></DIV>