#include "oplsaa.ff/forcefield.itp"

; original reference: [M. W. Mahoney and W. L. Jorgensen, J. Chem. Phys. 112 , 2000]
;
; Note that there are various issues with tip5p and the different forcefields.
; Discussion is here: https://gitlab.com/gromacs/gromacs/-/issues/1348

[ moleculetype ]
; molname       nrexcl
SOL             2

[ atoms ]
; id    at type res nr  residu name     at name         cg nr   charge
1       opls_118     1       SOL              OW             1       0
2       opls_119     1       SOL             HW1             1       0.241
3       opls_119     1       SOL             HW2             1       0.241
4       opls_120     1       SOL             LP1             1      -0.241
5       opls_120     1       SOL             LP2             1      -0.241

[ bonds ]
; i     j       funct   length  force.c.
1       2       1       0.09572 502416.0 0.09572        502416.0
1       3       1       0.09572 502416.0 0.09572        502416.0

[ angles ]
; i     j       k       funct   angle   force.c.
2       1       3       1       104.52  628.02  104.52  628.02

[ virtual_sites3 ]
; The position of the virtual site is computed as follows:
;
; The distance from OW to L is 0.07 nm, the geometry is tetrahedral
; (109.47 deg)
; Therefore, a = b = 0.07 * cos (109.47/2) / | xOH1 + xOH2 |
;            c = 0.07 * sin (109.47/2) / | xOH1 X xOH2 |
;
; Using | xOH1 X xOH2 | = | xOH1 | | xOH2 | sin (H1-O-H2)
;       | xOH1 + xOH2 | = 2 | xOH1 | cos (H1-O-H2)
; Vsite pos x4 = x1 + a*x21 + b*x31 + c*(x21 X x31)

; Vsite from                    funct   a       b               c
4       1       2       3       4       -0.344908  -0.344908  -6.4437903493
5       1       2       3       4       -0.344908  -0.344908   6.4437903493

[ exclusions ]
1       2       3       4       5
2       1       3       4       5
3       1       2       4       5
4       1       2       3       5
5       1       2       3       4

[ system ]
1 TIP5P

[ molecules ]
SOL 1