1 #include "oplsaa.ff/forcefield.itp"
3 ; original reference: [M. W. Mahoney and W. L. Jorgensen, J. Chem. Phys. 112 , 2000]
5 ; Note that there are various issues with tip5p and the different forcefields.
6 ; Discussion is here: https://gitlab.com/gromacs/gromacs/-/issues/1348
13 ; id at type res nr residu name at name cg nr charge
14 1 opls_118 1 SOL OW 1 0
15 2 opls_119 1 SOL HW1 1 0.241
16 3 opls_119 1 SOL HW2 1 0.241
17 4 opls_120 1 SOL LP1 1 -0.241
18 5 opls_120 1 SOL LP2 1 -0.241
21 ; i j funct length force.c.
22 1 2 1 0.09572 502416.0 0.09572 502416.0
23 1 3 1 0.09572 502416.0 0.09572 502416.0
26 ; i j k funct angle force.c.
27 2 1 3 1 104.52 628.02 104.52 628.02
30 ; The position of the virtual site is computed as follows:
32 ; The distance from OW to L is 0.07 nm, the geometry is tetrahedral
34 ; Therefore, a = b = 0.07 * cos (109.47/2) / | xOH1 + xOH2 |
35 ; c = 0.07 * sin (109.47/2) / | xOH1 X xOH2 |
37 ; Using | xOH1 X xOH2 | = | xOH1 | | xOH2 | sin (H1-O-H2)
38 ; | xOH1 + xOH2 | = 2 | xOH1 | cos (H1-O-H2)
39 ; Vsite pos x4 = x1 + a*x21 + b*x31 + c*(x21 X x31)
41 ; Vsite from funct a b c
42 4 1 2 3 4 -0.344908 -0.344908 -6.4437903493
43 5 1 2 3 4 -0.344908 -0.344908 6.4437903493