use of GMH in TDFT

[Oleksii]

Dear NWChem developers,

While exploring the source code of TDFT, I have come across the lines corresponding to the calculation of the electron coupling coefficient (Hab) using Generalised Mulliken-Hush theory:
#if 0
c
c        Calculate GMHCoupling Hab = mij*Eij/dsqrt((deltamu)**2 + 4*mij*mij)
         mij = dsqrt(tmom(2)**2+tmom(3)**2+tmom(4)**2)
         deltaEij = apbval(n)
         if (dabs(mij).le.mijtol) mij = 0.d0
         mijdeltaEij = mij*deltaEij
         deltamuij2 = (gsmom(2)-exmom(2))**2
     &              + (gsmom(3)-exmom(3))**2
     &              + (gsmom(4)-exmom(4))**2
         hab = mijdeltaEij/dsqrt(deltamuij2 + 4.d0*mij*mij)
         if (ga_nodeid().eq.0) then
                write (LuOut,*)
                write (LuOut,9252) dabs(hab)
                write (LuOut,*)
         endif
#endif

After uncommenting this block, recompiling the TDDFT module,  and insertion the "gmh" keyword in the configuration file, I was able to make the respective calculation run (have not yet done a proper benchmark though).

Can you please let me know if there are any caveats to using this module? It is also completely missing in the documentation.

Best regards,
Oleksii