# angle_style harmonic unit

Dear all,

I have a quick question with regard to the unit.

In unit real (http://lammps.sandia.gov/doc/units.html), we use Kcal/mole for energy term. In angle_style harmonic (http://lammps.sandia.gov/doc/angle_harmonic.html), we use energy/radian^2 for parameter K and degrees for theta0. (Note from LAMMPS: Theta0 is specified in degrees, but LAMMPS converts it to radians internally; hence the units of K are in energy/radian^2.)

For example, angle_coeff 1 300.0 107.0 means K = 300 energy/radian^2 and Theta0 = 107.0 degree.

Here comes the question.
From one of the literature, they use k_theta = 210.6803 (kcal/mol degree^2) and theta0 = 109.5665 (degree) in their angle bending term E_a(theta) = 1/2 * k_theta * (theta - theta0)^2

I think I should transfer the unit of k_theta from (kcal/mol degree^2) to (kcal/mol radian^2), which is 1 (kcal/mol degree^2) = 57.296^2 (kcal/mol radian^2).

It gives me angle_coeff 1 691628 109.5665

Am I do it right? The huge number 691628 in K seems strange to me. Thanks.

Cheers,
F.S.