Dear LAMMPS users,
I want to use TIP4P/2005 water molecules in LAMMPS. I used Moltemplate with OPLS force field to create water.lt. I have tried the following two methods.
I would appreciate if I have your advice on the following questions/problems:
• Using the first method, I can run on GPU. However, I can run only on the CPU if I apply the second method. Is there any way to run it on GPU?
• In the first approach, the system initially has high energy and pressure, and minimization does not work. How to fix very high energy when minimization does not work?
• In the first approach, If I replace the fix rigid with a fix (not rigid) and use fix shake, the bonds and atoms are lost, and the simulation ends with an error. Does the result of fix shake + fix differ from fix rigid, or are they the same?
• Which of these methods is correct and should be implemented?
First Method
I created water.pdb, including one oxygen, two hydrogens, and one massless atom. I set the charges, pair coefficients, pair style, and kspace style as follows. I then used fix rigid/npt in the simulation.
water inherits OPLSAA{
write(“Data Atoms”) {
$atom:O1 $mol @atom:65 0.00 0.0 0.00000 0.21451
$atom:H1 $mol @atom:66 0.00 0.0 0.75695 -0.37137
$atom:H2 $mol @atom:66 0.00 0.0 -0.75695 -0.37137
$atom:N1 $mol @atom:67 0.00 0.0 0.00000 0.05991
}
write(“Data Bond List”) {
$bond:O1H1 $atom:O1 $atom:H1
$bond:O1H2 $atom:O1 $atom:H2
$bond:O1N1 $atom:O1 $atom:N1
}
}
set type 65 charge 0 # oxygen
set type 66 charge 0.5564 # hydrogen
set type 67 charge -1.1128 # massless
bond_coeff 231 0.0 0.9572
pair_coeff 65 65 0.1852 3.1589
pair_coeff 66 66 0.0 0.0
pair_coeff 67 67 0.0 0.0
angle_coeff 475 0.0 104.52
angle_coeff 476 0.0 52.26
………………….
pair_style lj/cut/coul/long 12 14
……………………
kspace_style pppm 1e-5.0000
Second Method
I created water.pdb, in which the position of three atoms, including one oxygen and two hydrogens. I applied both of these pair styles: lj/cut/tip4p/long/ and lj/cut/tip4p/long/gpu
COMPND UNNAMED
AUTHOR GENERATED BY OPEN BABEL 2.3.90
HETATM 1 O HOH 1 0.000 0.000 0.215 1.00 0.00 O
HETATM 2 H HOH 1 0.000 0.757 -0.371 1.00 0.00 H
HETATM 3 H HOH 1 0.000 -0.757 -0.371 1.00 0.00 H
CONECT 2 1
CONECT 3 1
END