Covalent angles

Covalent angles are described by harmonic potential of the angle:

$$U_{ang}(\theta) = k_{\theta}(\theta - \theta_0)^2$$ (6)

where $\theta_0$ is the equilibrium angle and $k_{\theta}$ is the force constant.

The first line specifies the number of angles.

Next lines give parameters of angles. The fields of each line have the follow meanings:

1),2) and 3) define atom numbers

4) is the equilibrium angle in degrees

5) is the force constant in kJ/mol/rad**2

Note. The CHARMM force field has the so-called Urey-Bradley term which is a harmonic interaction between 1-3 neighbors. This term can be introduced in the list of bonds.