[gmx-users] Fwd: amber03 force field

[Mark Abraham]

X-C-CN-X is not present in amber03 in the GROMACS distribution. You seem to
be using some modified version. Please ask the person who modified it :-)

Mark


On Wed, Apr 24, 2013 at 4:26 PM, Elisa Frezza <elisa.frezza at gmail.com>wrote:

> Dear All,
>
> I am starting to use amber03 force field, but I have found something very
> strange for proper angle dihedral.
>
> On the basis of definition of proper dihedral function in AMBER and GROMACS
> manual I aspect that the following conversion from amber to gromacs:
>
> k_n(GROMACS)=4.18/2 V_n (AMBER)
>
> where n= multiplicity.
>
> If I compare ffbonded.itp file in ffamber03 folder and the parameter
> reported in amber I find something very strange and I do not understand
> what it is right:
>
>                                                    constant       angle
>    multiplicity
> AMBER:       X   C    CN    X            8.00         180                 2
> GROMACS   X   C    CN    X          16.736        180                 2
>        # kn= 4.18/2 V_n
>
>                                                    constant       angle
>    multiplicity
> AMBER:       X   C    NA    X            5.648         180
> 2
> GROMACS   X   C    NA    X            5.648         180                 2
>          # kn= 4.18/4 V_n
>
> the ratios between kn and Vn are different.
> Have someone some suggestions or explanation?
>
> Thanks in advance
>
> Elisa
>
> --
> Elisa Frezza
> Ph.D. Student in Materials Science and Engineering
> Dipartimento di Scienze Chimiche
> Università di Padova
> via Marzolo, 1
> 35131 Padova - Italy
> Phone: +39 049 827 5149
> Skype: elisa.frezza
> Emai: elisa.frezza at gmail.com
>          elisa.frezza at studenti.unipd.it
>
>
>
>
>
> --
> Elisa Frezza
> Ph.D. Student in Materials Science and Engineering
> Dipartimento di Scienze Chimiche
> Università di Padova
> via Marzolo, 1
> 35131 Padova - Italy
> Phone: +39 049 827 5149
> Skype: elisa.frezza
> Emai: elisa.frezza at gmail.com
>          elisa.frezza at studenti.unipd.it
> --
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