vibrational modes for WS2

We can solve the vibrational modes from the Hamiltonian of classical mechanics.

Assuming:

1) There is one spring constant k, and two kinds of masses: m for S and M for W.

2) The coordinates are (x1,y1) and (x2,y2) for S and (x3,y3) for W.

Using {x1,y1,x2,y2,x3,y3} as basis, we can get the matrix:

,

Mode set one:

Mode set two (translation):

Mode set three: