Besides, I could use " -ignore " command to ignore the hint information, and the translation work could be implemented successfully, but the datefile for Lammps doesn’t include just the angle information of forcefield parameters.
According to my knowleged, the natural rubber is composed of just the basic C and H elements, all the elements and bonds is simple, and the CVFF is expected to be qualified for setting all the forefield parameters needed when using msi2lmp tool. But the rock is on the road. I am comfused now, and need your help. Than you in advance for any advices and comments.
The “rubber.car” and “rubber.mdf” is enclosed in the style of attachment.
Hi, dear Lammps Users,
Using msi2lmp tool to construct the datafile of natural rubber, the
important hint informatin came out as follows,
"Unable to find angle data for c2 c2 c="
And then , the msi2lmp.exe disables and stops the process of
translating the molecular model made by Accelrys Materials Studio (MS) into
LAMMPS datafile.
I have some tries:
(A) I think that's the problem is caused by missing the "angle data
for c2 c2 c=" in cvff, because I can't find the angle information inside the
original text file of "cvff.frc" by myself.
(B) After I copy the cvff.frc from MS to substitute the cvff.frc in
the msi2lmp tool, the same error came out. That 's probably because both the
cvff.frc files in MS and msi2lmp tool are the same.
(C) However, it is strange that the MS Discover could complete the
simple MD computation with CVFF. The compuation test proves that the MS
could find the information of angle data for "c2 c2 c=" in cvff.frc
no, it does not prove that it can find the parameter set. whether an
MD code "runs" proves nothing. how do you know that it doesn't ignore
the missing terms? some programs are written like that. in fact,
msi2lmp was written like that initially. i changed it and introduced
the -ignore flag, so that you as the user gets to know and has to make
a conscious choice whether to ignore the missing parameters or not.
Thus far, I want to inquiry, based on the same cvff.frc, why the MS
can find "the angle informatin for c2 c2 c=" but the msi2lmp tool can NOT,
and whether the angle parameters on earth exists in cvff.frc.
Besides, I could use " -ignore " command to ignore the hint
information, and the translation work could be implemented successfully, but
the datefile for Lammps doesn't include just the angle information of
forcefield parameters.
According to my knowleged, the natural rubber is composed of just the
basic C and H elements, all the elements and bonds is simple, and the CVFF
is expected to be qualified for setting all the forefield parameters needed
when using msi2lmp tool. But the rock is on the road. I am comfused now, and
need your help. Than you in advance for any advices and comments.
i don't see currently any need for action as far as msi2lmp is concerned.
i would suggest you try to run tests with MS, ideally with a
simplified structure that can prove whether it correctly assigns the
angle as you currently think it does and then - if possible - try to
identify what parameter set is used. you (we) could then use that to
"patch" the CVFF.frc file
Dear Axel,
Thank you for your advice. Yes, the angle data is not included in the file named cvff.frc.
In Matirial Studio, the cvff also the ability to use automatic parameters (automatic assignment
of values for missing parameters) when no explicit parameters are present. However, the missing
forcefield parameter could not be set automatically in LAMMPS.
In the last part of your comments, you advice me
“try to identify what parameter set is used. you (we) could then use that to"patch” the CVFF.frc file".
But I know little how to obtained the critical parameters. Would you please give more details.
Dear Axel,
Thank you for your advice. Yes, the angle data is not included in
the file named cvff.frc.
In Matirial Studio, the cvff also the ability to use automatic parameters
(automatic assignment
of values for missing parameters) when no explicit parameters are present.
However, the missing
forcefield parameter could not be set automatically in LAMMPS.
no, because this is a feature that i consider a bad practice. in
LAMMPS this is not done for a good reason. people need to know what is
happening. if you want to insert "generic" parameters, you can do this
manually yourself.
In the last part of your comments, you advice me
"try to identify what parameter set is used. you (we) could then use that
to"patch" the CVFF.frc file".
But I know little how to obtained the critical parameters. Would you please
give more details.
no. i don't have materials studio and thus have no way to give any
details beyond what i said.