How to fix O-H bond

[Junbo Lu]

Hello everyone,

  I need to fix the O-H bond for my system. I have searched the previous post. It seems that we just need to write such entry in MOTION section:
   &CONSTRAINT

    &HBONDS

    &END HBONDS

  &END CONSTRAINT

   Do we need to set other parameters? Could anyone give a help? I would be very appreciated!

   With my best regards,

  Junbo

[Dawid das]

Hi,

This part of input will simply constrain all bond lengths at their initial value given the bond is between H and any other atom. I think that it is only important that atom name type starts with H. Otherwise it is not recognized as a hydrogen.

[Junbo Lu]

Hi,

  Thank you very much! Do you have some detailed input? I have seen the manual about this section, but I am still confused with some keywords:

  (1) How do we set ATOM_TYPE? Do I need to set MOLNAME and MOLECULE? It seems that these two keywords are about QM/MM. My system contains a lot of H2O, OH- and Na+, and the coordination section is:

Na    9.215   6.592   1.668

Na   14.130  14.360   2.607

O     9.966  14.063  13.214

H     9.488  14.543  12.480

H    10.743  13.638  12.750

O    13.501   5.419  14.746

H    13.691   5.028  13.845

H    12.615   5.047  15.023

O     7.910   9.825   6.157

H     7.948   9.265   5.391

O     7.189   5.650   9.573

H     6.475   5.731   8.952

...

  (2)  In my system, the Na has no bonds with H. If I just use such simple input entry,  will the Na-H bond be fixed?

  With my best regards,

  Junbo

'Dawid das' via cp2k <cp...@googlegroups.com> 于2021年11月29日周一 上午2:19写道：

Hi,

This part of input will simply constrain all bond lengths at their initial value given the bond is between H and any other atom. I think that it is only important that atom name type starts with H. Otherwise it is not recognized as a hydrogen.

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