# Import the KohnSham module from ATK
from ATK.KohnSham import *

# Define function for handling molecule setup   
def waterConfiguration(angle,bondLength):
    from math import sin,cos
    
    theta = angle.inUnitsOf(radians)
    pos = [(0.0, 0.0, 0.0)*Angstrom,
           (1.0, 0.0, 0.0)*bondLength,
           (cos(theta), sin(theta), 0.0)*bondLength]
    elm = [Oxygen] + [Hydrogen]*2
    
    return MoleculeConfiguration(elm,pos)

   
# Choose DFT method
method = KohnShamMethod()

# Scan different bending angles and calculate energy
for i in range(30,181,5):
    theta = i*degrees
    h2o = waterConfiguration(theta, 0.958*Angstrom)
    scf = method.apply( h2o )
    print 'Angle = ', theta, ' Total Energy = ',calculateTotalEnergy(scf)