[gmx-users] phosphate ion force field again!

[nanyu101 at sina.com]

Dear gmx-users,
   Thanks for your telling me about the phosphate ion's force field.Now I have a different case about phosphate ion. There is a Pi32 linear chain, and I want to take the middle of this chain as an identical phosphate ion. In the Dr D. van der Spoel's literature, the polyphosphate such as Pi4 and Pi8 was taken as a whole molecule. In my case, I want to devide the chain into three types,every phosphate ion in the polyphosphate was seen as a unit. So I need to do some regulations on the previous force field! I have tried to learn the method in the literature and failed in cracking it. My method was listed as follows.

%chk = phosphate
#b3lyp/6-31++g** opt SCRF(Dipole,A0=3.58,Dielectric=78.5) Pop=MK

phosphate ion atomic charge

-1  1
P 0    0.283081    0.236649    0.418137
O 0    1.531021   -0.506180   -0.280106
O 0   -0.035156   -0.804382    1.604141
O 0   -0.899780   -0.129669   -0.613144
O 0    0.455368    1.658554    0.790207
H 0    1.756866   -0.038971   -1.088440
H 0   -0.845230   -0.531906    2.041702

I do not know what the wrong is. Would you please give some advices? Thanks a lot.
Best wishes,
nanyu

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