Calculate the dihedral angle using four points.

dihedral [<name>] <mask1> <mask2> <mask3> <mask4>
         [out <filename>] 
         [type {alpha|beta|gamma|delta|epsilon|zeta|chi|c2p|h1p|phi|psi|omega|pchi}]

[<name>] Output data set name.
<maskX> Four atom masks selecting atom(s) to calculate dihedral for.
[out <filename>] Output file name.
[mass] Use center of mass of atoms in <maskX>; default is geometric center.
[range360] Output dihedral angle values from 0 to 360 degrees instead of -180 to 180 degrees.
[type <type>] Label dihedral as <type> for use with statistics analysis; note chi is nucleic acid chi and pchi is protein chi.

Calculate dihedral angle (in degrees) between the planes defined by atoms in <mask1>, <mask2>, <mask3> and <mask2>, <mask3>, <mask4>. To calculate multiple dihedral angles see the multidihedral command.