Dear users,
My apologies for the late reply. I have been on vacation for the past three weeks. I was not aware of the issues with OPLS-AA. In the meanwhile, I have created a 2024 version of OPLS-AA, which uses bond increments for partial charge assignment. This allows for a more general and flexible force field. I would suggest to install the following two files
opls-aa.prm (62.2 KB)
opls-aa.top (13.3 KB)
in $EMC_ROOT/field/opls/2024. This allows them to be accessed through field opls/2024/opls-aa as is illustrated by the following example:
# Options section
ITEM OPTIONS
replace true
field opls/2024/opls-aa
density 0.1
radius 10
nrelax 500
number true
focus true
pdb_licorice true
emc_execute true
ITEM END # OPTIONS
# Groups section
ITEM GROUPS
m1 *c1ccc(cc1)*, 1, m1:2
t1 *c1ccccc1, 1, m1:2
t2 *c1ccccc1, 1, m1:1
ITEM END # GROUPS
# Clusters section
ITEM CLUSTERS
polymer alternate,1
ITEM END # CLUSTERS
# Polymers section
ITEM POLYMERS
polymer
1 m1,10,t1,1,t2,1
ITEM END # POLYMERS
I have increased radius and nrelax since polyphenylene is rather stiff. Note that OPLS-AA has a native type C! for bridging aromatic carbons between two phenyl rings which is captured by type c3ab in OPLS-AA 2024.
I will have to upload a new version of EMC, since the current version does not understand ^6 ring designations in rules well. I will post an update here, once this new version has been uploaded for all compilation targets. This 2024 version of OPLS-AA is still experimental. Please let me know, if you experience any issues.
For the 2012 version of OPLS-AA one can use the files as provided by the 2023 release of EMC:
opls-aa.prm (34.9 KB)
opls-aa.top (30.0 KB)