phonon_coupling: Phonon Coupling Position and Strength Calculation
In tjconstant/grapheneSPP: Graphene SPP Dispersion Calculation

Function to return surface phonon frequencies and coupling coupling coefficents for dispersion

1 2	phonon_coupling(q, omega, d = 3.5e-10, omega_TO, omega_LO, eps_graphene = 3.9, eps_substrate = 2.4)

`q`	wavevector [m^-1]
`omega`	angular frequency [s^-1]
`d`	distance between graphene and substrate [m]
`omega_TO`	vector of frequencies of transverse optical phonons [cm^-1]
`omega_LO`	vector of frequencies of longitudinal optical phonons [cm^-1]
`eps_graphene`	static permittivity
`eps_substrate`	permittivity at infinity / high frequency dielectric constant (also refered to elsewhere as eps_inf)