Bond Length: The distance between the centers of two nuclei of atoms connected by a chemical bond is known as ‘bond length’.
Bond Angle: The angle between the directions of two bonds in a molecule is called the ‘bond angle’.
Bond angle depend upon factors,
(i) charge distribution, (ii) geometry of the molecules, (iii) symmetry, (iv) hybridization etc.
To calculate the power spectrum of water you need multiple variables, using only the bond acacuracy of power spectrum would be reduced.
Include electronegativity, atomic number etc to increase accuracy.
The bond energy of the covalent O−H bonds in water is said to be 110.3 kcal/mol (461.5 kJ/mol), the bond angle is 105 deg.
since deviation causes loss of energy, you could use a basic relational formula for dissociation to calculate power spectrum like :
bond_strength = 110.3-((bond_angle_of_water - 105)^2)*bond_angle_of_water/105;