Angle and Bond style Value in Lammps

[Arman1578]

Hello everyone
Please help me
In first picture that I’ve shared with you , we have harmonic angle style formula that included 1/2 factor.
1- I wanna know , when I want use different force field like OPLS that I’ve shared in second picture, there is different formula with lammps : E=K(r-r0)^2 ,Do I need to double the value of K from OPLS ,then I place it at the input file?

2- What should I do in other states , for example , when force field’s formula is E=1/2K(r-r0)^2

3-How about third picture? it is another force field with different formula : 1/2K(teta -teta0)
In this formula, we do not have a power of 2. for the harmonic style What changes should I make?

I would appreciate your guidance on these three questions.

[akohlmey]

@Arman1578

Do I need to double the value of K from OPLS ,then I place it at the input file?

Why? The formula for the potential energy is exactly the same in (1) and (2).

@Arman1578

What should I do in other states , for example , when force field’s formula is E=1/2K(r-r0)^2

That is an elementary calculus problem. You have E = \frac{1}{2}K_1(r-r_0)^2 and E = K_2(r-r_0)^2. Now you just need to determine the relation between K_1 and K_2.

@Arman1578

What changes should I make?

First thing is to determine whether this is a typo in paper or the real potential.

[Arman1578]

Thank you.