constraining bond lengths and other internal coordinates via ICONST

[awang95]

Hi,

Following this post (forum/viewtopic.php?f=4&t=18723&p=22915#p22915), I'm wondering would there also be an implementation to combine ICONST with IBRION = 1, 2 for constraining specific bond lengths, angles, and dihedral angles (which would be really useful for studying certain adsorbate-surface interactions)? If so would it be possible to ask when it might be available?

Thanks!

[ralf_tonner1]

Hi awang95,
Have you considered setting the 'Selective dynamics' feature in the POSCAR for this task? This feature allows to fix the coordinate(s) of specific atoms during the ionic relaxation. If you do not relax the appropriate atoms, that automatically constrains the specific bond lengths and angles.

[awang95]

yes I have considered it, but there are situations where the internal coordinates (i.e. bond lengths, angles, or dihedral angles) of a molecule can stay fixed while allowing x, y, and z to move (i.e. all atoms in the molecule translating or rotating together), so ideally it would be nice to still set "T" in selective dynamics while constraining for example the bond length of a molecule - is there any chance that this could be implemented in a future release? thanks

[alexey.tal]

Dear awang95,

This option of using ICONST with IBRION=1,2 is not yet available in VASP and I can't really give you a timeline for when it will be implemented. But it is on a list of features that we are planning to add I will post an update in this thread when we release it. Meanwhile, I can suggest that you try to run an MD simulation with ICONST and quench the temperature to 0K.

[awang95]

ok thanks!