The two-center one-electron integral H_mn  

Sometimes called the resonance integral, H_mn is approximated using the overlap integral, S_mn . Note that this violates the NDO approximation, but since resonance integrals are large, this integral is retained. This is the origin of Modified in the name of the method. With Slater atomic orbitals of type

f_m  = Nr^n-1e^-xr

the overlap integral is given by:

S_mn  = <f_mf_n>.

H_mn is approximated by:

H_mn  = S_mn1/2(b_m + b_n);