Handle missing rules using OPLS FF

EMC
1

Hi users,

I am trying to create a polymer melt and it works perfectly fine using PCFF parameters. However, it gives error with OPLS FF.

Any help to overcome this would be highly appreciated.

Thanks,
Karteek

2

Can you post the error?

3

Hi,
Thanks for the response. Here is the error message associated with OPLS FF files.

Warning: missing rules for field ‘~/Desktop/Toyota/SPE/EMC/v9.4.4/field/opls/2012/opls-aa.prm’.
Warning: missing rule for {group, site} = {PPS, 8}.
Error: core/fields.c:432 FieldsApply:
Missing rules.
Program aborted.

Thanks,
Karteek

4

Hi Karteek,

This indicates, that – during typing – a rule is missing for specific chemical environment in your molecule, here at site 8 of cluster PPS. SMILES snippets represent these rules. Without knowing more about your chemical structure, I would suggest finding out what exactly is missing by adding ‘field_debug reduced’ under ‘ITEM OPTIONS’. This generates which rules are successfully applied and which not. Based on this information, you could design an additional rule, if you know, which atom type your chemical environment should have. You can either manually add this rule to the associated topology file, in your case ‘opls-aa.top’ in ‘~/Desktop/Toyota/SPE/EMC/v9.4.4/field/opls/2012/’, or add the missing information to ‘opls-aa.define’ and execute ‘convert.sh’ while in the same directory. I personally prefer the latter.

Pieter