# Calculations of the charge transfer in GAMESS US

I'm trying to calculate the effective transfer integrals $$J_{\text{eff}}$$ from monomer A to monomer B within dimer AB by using GAMESS US: $$J_{\text{eff}}=\frac{J-S\cdot (e_1+e_2)/2}{1-S^2},$$ where $$e_1=\langle\phi_1|H^{KS}|\phi_1\rangle$$, $$e_2=\langle\phi_2|H^{KS}|\phi_2\rangle$$, $$J=\langle\phi_1|H^{KS}|\phi_2\rangle$$ (charge transfer integral), $$S=\langle\phi_1|\phi_2\rangle$$ (overlap integral), $$\phi_1$$ - LUMO or HOMO of monomer A, $$\phi_2$$ - LUMO or HOMO of monomer B.

Does anybody know a step-by-step tutorial how to do that with GAMESS US?

• I don't know if GAMESS can do it directly, but I have to imagine it can print the Fock and overlap matrices, allowing you to compute $J_\text{eff}$ manually.
– Tyberius
Sep 21 at 16:59
• +1 and welcome to our new community! Thank you for contributing your question here and we hope to see much more of you in the future !!! Oct 19 at 20:32
• Also, a related publication about computing couplings for bridged dimers: pubs.acs.org/doi/10.1021/acs.jctc.7b00431. You can treat the monomers as separate, but this would also allow you to treat possible overlapping fragments.
– Tyberius
Nov 3 at 17:02