to obtain rates of charge transfer you typically need to calculate diabatic electronic coupling matrix element between two charge-localized states. There are various approaches to do so. Within DFT framework there are various approaches like constrained DFT (CDFT) or economic fragment-orbital based DFT. Wave function based methods also offer way to obtain diabatic states e.g. via generalized Mulliken-Hush method (GMH). You might have a look at following papers:

CDFT in atom-centred basis sets:

Wu and Van Voorhis, Phys. Rev. A 72, 024502 (2005)

Wu and Van Van Voorhis, J. Chem. Phys. 125, 164105 (2006)

CDFT and FODFT in plane-waves (like in VASP but this is CPMD implementation):

Oberhofer and Blumberger, J. Chem. Phys. 131, 064101 (2009)

Oberhofer and Blumberger, J. Chem. Phys. 133, 244105 (2010)

GMH

Cave and Newton, J. Chem. Phys. 106, 9213 (1997)

We recently published a benchmark paper which compares various approaches for the electronic coupling matrix elements:

Kubas, Hoffmann, Heck, Oberhofer, Elstner, Blumberger, J. Chem. Phys. 140, 104105 (2014)

http://scitation.aip.org/content/aip/journal/jcp/140/10/10.1063/1.4867077

Hope this helps.

best wishes,

Adam

Danylo,

It depends on what you want to know. If you just want a value for the charge transfer then, most simply, you could perform your DFT calculation in the presence and absence of the electric field and compare atomic charges using NBO or QTAIM analysis. This would give you a measure of the charge transfer. If you're interested in dynamics though, you need a more sophisticated approach , as Adam points out.

Adam and Andrew, thanks for your answers and suggested papers, especially for the comparison paper.

More precisely, I have a system I-II-I (I-big molecule, II - small molecule) and need to calculate charge transfer rate between I and I via II. What do you think about Marcus theory?

Hi Danylo

for a well-localized states this should typically work quite well. However, to match with experiment you probably need to account for the dynamics of the system and the response of the environment, perhaps via some kind of MD. More technical aspects will strongly depend on the system studied (size, nature etc.).

For Marcus-theory related problems you may have a look at this paper (especially into and thory parts) and references therein:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2924466/

Best wishes,

Adam

Formula for charge transfer is:

q = it