Computing electron transfer matrix element or electron transfer integral (H_ab) using a Generalized Mulliken−Hush (GMH) in NWChem program.

Herein, tddft module has been being modified to compute electron transfer matrix element using GMH method based on following formula.

                (Ej - Ei) * muij
GMH = ------------------------------------
         _______________________________
       \/ (muii - mujj)**2 + 4*(muij**2)

where E_i and E_j are energy for each pair of ground state and excited state, and mu_ii, mu_jj, and mu_ij are transition dipole moments for different species of the system.

• Doxygen for NWChem documenting
• Generalization of the Mulliken-Hush treatment for the calculation of electron transfer matrix elements Author links open overlay panel by Robert J.Cave et al.
• Computational Methods For Electronic Couplings by Chao-Ping Hsu, Academia Sinica

This GMH approach is experimentally modified based on original source codes of Time-Dependent Density Functional Theory (all tddft_*.F files) of NWChem software which were written by Prof. So Hirata. I am not responsible for any damage caused through use of all products here.

The latest version of writing this document is NWChem 6.8.1, which is released as open-source under the ECL 2.0 license.

First, I strongly suggest you to compile NWChem with full packages. Then you can recompile NWChem with my modified GMH source code. Please following the steps below for a successful recompilation of your NWChem integrated with my modified GMH module.

Step 1. Replace TD-DFT source code with a modified GMH source code (you should backup all original source codes as well.)

$NWCHEM_TOP/src/etrans

where $NWCHEM is set to NWChem top directory.

Step 2. Go to folder where source code is modified.

cd $NWCHEM_TOP/src/etrans

Step 3. Setting up environmental variable as if first time you compile NWChem. The following is a portion of NWChem compile bash script.

export USE_64TO32=y
cd $NWCHEM_TOP/src/etrans
make
cd $NWCHEM_TOP/src
make link
echo "Done"

Example bash script can be obtained: recompile-nwchem.sh.

Step 4. A new NWChem executable nwchem will replace the old one.