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Atomic Position Relaxation Results in unequal Bond Lengths

Posted: Wed Mar 13, 2024 6:11 pm
by asgharali_jan
I want to calculate elastic constants of RuBr2, material with MoS2 like structure and when I perform atomic relaxation using ISIF = 2...my structure badly changes and bond length between Ru and two Br atoms becomes unequal and one Br atom also moves out of central axis. I want that both bond lengths should be equally changed

Re: Atomic Position Relaxation Results in unequal Bond Lengths

Posted: Mon Mar 18, 2024 10:20 am
by andreas.singraber
Hello!

Please be more specific about your problem and attach input and output files according to the forum posting guidelines.

As far as I know it is not possible to apply constraints while running relaxation with IBRION > 0. Maybe you intended to change only the cell shape and/or volume while keeping the structure? If so, then have a look at the ISIF table and try with ISIF = 5, 6, 7.
In molecular dynamics (IBRION = 0) you can use the ICONST file to fix the bond lengths between selected atoms.

Best,
Andreas Singraber