CHARMM Development Project
Posted By: Methuselah 1-4 vdw interaction - 11/12/09 01:51 PM
I notice that in Charmm parameter files some atoms have two sets of vdw parameters - one for the 'normal' vdw interaction and the other for 1-4 vdw interaction. For example:

C 0.000000 -0.110000 2.000000 ! ALLOW PEP POL ARO
! NMA pure solvent, adm jr., 3/3/93

and
CT1 0.000000 -0.020000 2.275000 0.000000 -0.010000 1.900000 ! ALLOW ALI
! isobutane pure solvent properties, adm jr, 2/3/92

My question is this: if an atom does not contain the second set of parameters (such as C as shown above), does Charmm still include the 1-4 interactions for an atom pair that contain atom C?
Posted By: lennart Re: 1-4 vdw interaction - 11/12/09 01:56 PM
yes
Posted By: Methuselah Re: 1-4 vdw interaction - 11/12/09 02:47 PM
If so, which set of parameters is it using? Is it the first set?
Posted By: lennart Re: 1-4 vdw interaction - 11/12/09 04:00 PM
If the second set is missing the values from the first set are used as 1-4 parameters for that atomtype.
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