Hi Axel,
I had a couple of quick questions regarding maps and emc2.
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I’m doing a maps runs on the bcc form of MgSc. However, two problems arise. The first is that while the majority of the structures fall nicely within the convex hull, a handful of structures fall far below it in terms of energy. Looking at the vasp output shows the warning "hit a member that was already found in another star". For some of the structures I can "fix" the problem (return the energy to a more reasonable value) by moving the atomic positions by small amounts (either manually or via cellcvrt -jc or -ja). Do you have any intuition why this phenomena might occur, and is there a better way to fix it. I’ve also found that setting ISYM=0 can fix the problem, but I don’t know if this has other negative consequences.
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Related to the last question, even after doing the "atomic jiggling" I find that the checkrelax scores for my structures are not ideal. In the manual it says anything above a relax score of 0.1 should not be included, but roughly 1/3 of my MgSc bcc structures have checkrelax scores higher than 0.1 (most fall in the range 0.1-0.4). The highest scores belong to those structures which I "fixed" (as discussed above). I would just remove all these offending structures, but I worry because I feel it will remove much necessary information from the cluster expansion, especially when the offending structures only have ~3 atoms. Do you have any thoughts about the best way to proceed with this problem?
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Finally, relating to emc2: I understand almost all of the rationale behind the -mu0 and -mu1 tag values. However, I am a little confused what it means to have -mu0 or -mu1 be negative (when the -abs tag is NOT set). Could you please explain?
Thank you.