Covalent angles are described by harmonic potential of the angle:

where is the equilibrium angle and 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.

Alexander Lyubartsev 2015-02-06