[gmx-users] Using SPC/E water with the OPLS force field

[Miguel Caro]

Hello everyone,

I am trying to use SPC/E water with the OPLS force field (I took the
OPLS itp file available from virtualchemistry.org). There is a number of
OW and HW atoms available (list below). At the moment I have chosen
opls_111 and opls_112, respectively. Is there any "standard" pair that
should be used? If I understand it correctly, the partial charges will
be overwritten by the molecule topology, but the LJ parameters will be
taken from the OPLS topology, so should I expect big differences if I
use, e.g. opls_116 and opls_117?

Thanks,
Miguel

    #ifdef HEAVY_H
     opls_111   OW  8      9.95140    -0.834       A    3.15061e-01 
    6.36386e-01
     opls_112   HW  1      4.03200     0.417       A    0.00000e+00 
    0.00000e+00
     opls_113   OW  8      9.95140     0.000       A    3.15365e-01 
    6.48520e-01
     opls_114   HW  1      4.03200     0.520       A    0.00000e+00 
    0.00000e+00
     opls_115   MW  0      0.00000    -1.040       D    0.00000e+00 
    0.00000e+00
     opls_116   OW  8      9.95140    -0.820       A    3.16557e-01 
    6.50194e-01
     opls_117   HW  1      4.03200     0.410       A    0.00000e+00 
    0.00000e+00
    #else
     opls_111   OW  8     15.99940    -0.834       A    3.15061e-01 
    6.36386e-01
     opls_112   HW  1      1.00800     0.417       A    0.00000e+00 
    0.00000e+00
     opls_113   OW  8     15.99940     0.000       A    3.15365e-01 
    6.48520e-01
     opls_114   HW  1      1.00800     0.520       A    0.00000e+00 
    0.00000e+00
     opls_115   MW  0      0.00000    -1.040       D    0.00000e+00 
    0.00000e+00
     opls_116   OW  8     15.99940    -0.820       A    3.16557e-01 
    6.50194e-01
     opls_117   HW  1      1.00800     0.410       A    0.00000e+00 
    0.00000e+00
    #endif
     opls_118   OW  8     15.99940     0.000       A    3.12000e-01 
    6.69440e-01
     opls_119   HW  1      1.00800     0.000       A    0.00000e+00 
    0.00000e+00

-- 
*Dr. Miguel Caro*
/Postdoctoral researcher/
Department of Electrical Engineering and Automation,
and COMP Centre of Excellence in Computational Nanoscience
Aalto University, Finland
Personal email: *mcaroba at gmail.com*
Work: *miguel.caro at aalto.fi*
Website: http://mcaroba.dyndns.org