[gmx-users] dipole moment of water using TIP3P model

[Sabreen Farnaz]

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?

If you could suggest me suitable references that might clarify this issue,
please let me know.

Thanks.