How do LAMMPS calculate force for TIP4P

Dear LAMMPS users,

Hello. I am studying LAMMPS and have a question about the TIP4P water model. The negative charge is put at a massless point rather than the oxygen atom. I know the molecular dynamics simulations are performed by solving a set of Newtonian equations. The velocity and accelerator of each atom is calculated to determine its position in next timestep. Then how could the electric force be applied at a massless point?


Kira Banks


The force is not applied at the massless point. The mechanism for measuring the forces is to calculate the forces at the location of the massless point, and then to redistribute it to the physical atoms. The full explanation of the method used, with all the equations and appropriate figures, is provided in the following paper:

Feenstra, K., Hess, B., & Berendsen, H. (1999). Improving efficiency of large time-scale molecular dynamics simulations of hydrogen-rich systems. Journal Of Computational Chemistry, 20(8), 786–798.