[gmx-users] (no subject)

[David]

On Thu, 2002-12-26 at 18:14, pqchen at eyou.com wrote:
> Dear gmx-users:
>   In Tinker pakages the improper torsion parameters are different from the
> parameters in gromacs pakages(opls-aa force field)?????
>   For example:
>   In Thinker pakages(opls-aa):
>   improper_Z_CA_X_Y       180.0      2.200(kcal/mol)   2
>   But in gromacs:
>   #define improper_Z_CA_X_Y       180.0      4.60548(KJ/mol)   2
> 
>   which is right?
> 
Apart from the factor 4.184 (x2.2 = 9.2048)
there seems to be a factor of two. This could be due to the different
definitions of the function. I don't know about tinker but in gromacs it
is
Vimp = 0.5 k_imp(xi - xi0)^2

There is a minute difference left due to the fact that we originally
used a different (wrong) definition of the cal > Joule conversion factor
(yes there are two, the other one is 4.1868!)
This is nothing to worry about, although it will be corrected in future
version of gromacs.

-- 
Groeten, David.
________________________________________________________________________
Dr. David van der Spoel, 	Biomedical center, Dept. of Biochemistry
Husargatan 3, Box 576,  	75123 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://xray.bmc.uu.se/~spoel
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