[gmx-users] Re:gromos torsion param

[rob yang]

never mind. I just read Erik's post. Thanks


>From: "rob yang" <nextgame at hotmail.com>
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>Subject: [gmx-users] Re:gromos torsion param
>Date: Wed, 18 Jan 2006 09:49:53 -0600
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>Thank you David.
>Does anybody have any experiences adding more torsion terms in gromos? What 
>would be the format in the .top files? Thank you in advance.
>
>Rob
>
>
>>From: David van der Spoel <spoel at xray.bmc.uu.se>
>>rob yang wrote:
>>>Hello,
>>>I've got a rudimentary question about gromos torsion parameters.
>>>
>>>the gromos parameter is of the following format:
>>>gd_1           2.67             -1.0            1
>>>name      force constant  phase shift    multiplicity
>>>
>>>>From the gromos paper, they've listed the torsion terms as
>>>K*[1+cos(phaseshift)cos(multiplicity*dihedral)
>>>
>>>In a given .top file, one would parameterize the torsion of i, j, k, l 
>>>by:
>>>i j k l gd_1
>>>
>>>so my question is that: does that mean for any torsion, there's only 
>>>*one* term associated with it in the gromos forcefield? In contrast,  
>>>oplsa allows up to 6 terms in the following form:
>>>V1/2(1+cos(x))+V2/2(1-cos(2x)) + V3/2(1+cos(3x))...
>>>
>>Yes that's correct, although you could in principle add multiple torsions 
>>I think.
>>
>
>
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