Dear all
I want to use COMPASS forcefield with EMC. The sourceforge website mentions that EMC can be used to generate input structures for COMPASS forcefield, but I’m unable to find a method to do so. The COMPASS forcefield is not available in the fields directory as well.
When I attempt to set the field to COMPASS, I get:
Warning: field ‘COMPASS’ not found
Any help in this regard is greatly appreciated.
Dear user,
COMPASS is a proprietary class 2 force, which is part of the Materials Studio package from Biovia (Dassault Systems). The force field uses the same syntactic input format as the PCFF force field. EMC can type COMPASS when the necessary input files are provided. However, due to the proprietary nature of COMPASS, the EMC does not include force field files for the COMPASS parameters and typing rules.
Dear Dr. Veld
Thank you for clarifying the situation with COMPASS and EMC.
Would it be possible to use the ‘compass_published.frc’ file bundled with LAMMPS for this purpose? If yes, is there any documentation for the same
Dear user,
Thank you for pointing out the existence of a published version of COMPASS. I assume you are referring to
$LAMMPS_ROOT/tools/msi2lmp/frc_files/compass_published.frc
in the LAMMPS distribution as can be found at the LAMMPS web site. You actually would have to split the compass_published.frc file into two by moving the templates section into its own separate templates file, because this file is mandatory. As it turns out, a number of end_test keywords are missing in the templates section. After adding these, this results in
compass.frc (59.3 KB)
compass_templates.dat (6.3 KB)
You can add these files either to your main force field collection by creating a compass directory in your EMC distribution,
$EMC_ROOT/field/compass
followed by copying the above two files here, or you can add them to the directory in which you are executing your EMC Setup script, or you can create a central depository somewhere else. In both latter cases you will have to let EMC Setup know where to find the force field files by setting the option field_location before you set field, which for a local copy would look like
ITEM OPTIONS
field_location .
field compass
ITEM END
You would leave out the field_location line, if you decide to add the compass files to your EMC distribution as described above. I successfully tested the validity of the above files. I will include this version of COMPASS in the next EMC release. Note that these files should also work with Materials Studio.
This paragraph was adapted and corrected after the questions and comments below.
Dear Dr. Veld
Thank you for your timely assistance on this matter. I’ll try it out and let you know if I face any issues.
Dear Dr. Veld
I’m encountering the following error when I use the COMPASS field as suggested. My aim is to build a polyethylene system of density 1 g/cc.
My EMC setup and build files are attached:
build.emc (4.4 KB)
pe_1.0.esh (343 Bytes)
Kindly look into the same.
Dear user,
I checked out the original and noticed some end_test keywords were missing in the original templates section. I corrected these mistakes and successfully tested the result. The updated the files can be found in my previous answer above.
Dear Dr. Veld
Thank you for your assistance and the quick turnaround on the issue.
