A new form Morse potential

Dear all users,

If I want to use a new form of Morse potential,

U=D {[1-exp[-σ(r_ij-r_o)]]^2 }=D[1+exp[-2σ(r_ij - r_o) - 2exp[-σ(r_ij - r_o) ], want should I do?

Compared with the formula in lammps, it has a constant part.

Sincerely

Yang

You can either tabulate it or code it up.

Ray

Does it really matter? The gradient of the potential is the same as the one implemented in LAMMPS, correct? So the dynamics you get are exactly the same, the only difference is in the absolute values of the potential energy, so you can correct this with post-processing.

Dear all users,

If I want to use a new form of Morse potential,

U=D {[1-exp[-σ(r_ij-r_o)]]^2 }=D[1+exp[-2σ(r_ij - r_o) - 2exp[-σ(r_ij - r_o)
], want should I do?

Compared with the formula in lammps, it has a constant part.

this is not different, but the same potential. absolute energy has no
meaning in classical MD, only relative energies.
the formulation you have is commonly used for bonds because it is
convenient to choose the energy at the minimum of the potential to be
zero for bonds, and thus it is used by the morse bond style as well.

axel.