On 5/9/19 6:54 AM, Sabreen Farnaz wrote:
Dear Users, It is known that electric dipole moment of a water monomer is experimentally 1.85 D and using the TIP3P model it's supposed to be 2.35D. I am using the TIP3P model for a water-based simulation in Gromacs 5.1.5. After applying sinusoidal electric fields in the Y axis, the norm of the dipole vector per water molecule using *gmx dipoles* is closer to 1.85 D and nowhere near 2.35D. My simulations are for 300K and 1 atm. Can anyone guess why the discrepancy? Is it because 2.35D is for a water monomer and my system has quite a large number of them(in the order of ten thousands)? But literature suggests that presence of water molecules should enhance the dipole moment. Or is 2.35D calculated under a different temperature/pressure conditions?
I don't know what your command was or how gmx dipoles might be calculating this quantity, but it is simply a fact that the dipole moment of rigid TIP3P is 2.35 D. It can't vary, by definition. You will not see any difference based on system size because the model is nonpolarizable - every TIP3P is identical, whether you have one or a million, so there is no dipole cooperativity.
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