I am building my first model of tip4p water with no boundaries, and I have a question about the charge parameter for the Oxygen atom listed on the lammps page for the tip4p model.
On the lammps page it states that the charge for the O atom for tip4p should be -1.04.
However in the reference paper listed on the lammps page. (Jorgensen et al. “Comparison of simple potential functions for simulating liquid water”, Journ. Chem. Phys vol 79, 1983),
in table 1, the charge for Oxygen is listed as 0.0, and the charge for the dummy site M is listed as -1.04, for the tip4p model.
Do I just go with the parameters on the lammps page, and put a charge of 0.0 on the M site?
These contradictory statements are very confusing, as I’m still just starting out at this.
Guidance greatly appreciated,
respectfully,
Hello, Daniel:
You do not create the dummy sites explicitly in LAMMPS, as the creation of a site with zero mass leads to errors in the calculation of accelerations. Instead, you use the parameters in the lj/cut/coul/long/tip4p specification to determine which atom type has the dummy charge. Assigning the charge to that atom, it gets transferred to the dummy atom by the code.
At the current time, however, I am debugging some issues associated with the virial calculations in the code. I hope to get those resolved in the next week or so.
–AEI
daniel,
I am building my first model of tip4p water with no boundaries, and I have a
question about the charge parameter for the Oxygen atom listed on the lammps
page for the tip4p model.
On the lammps page it states that the charge for the O atom for tip4p should
be -1.04.
However in the reference paper listed on the lammps page. (Jorgensen et al.
"Comparison of simple potential functions for simulating liquid water",
Journ. Chem. Phys vol 79, 1983),
in table 1, the charge for Oxygen is listed as 0.0, and the charge for the
dummy site M is listed as -1.04, for the tip4p model.
Do I just go with the parameters on the lammps page, and put a charge of 0.0
on the M site?
that depends on whether you are trying to build the tip4p model with
the default pair styles or use the tip4p optimized styles.
in the latter, you don't define the M site and both van der Waals
and charge are placed on the oxygen and then shifted to the
M position when needed.
cheers,
axel.