[gmx-users] Fwd: amber03 force field

[Elisa Frezza]

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