The RelPro project had the aim of implementing a computational technique for calculating non-linear optical molecular properties with a relativistic quantum chemistry method. Non-linear optical properties are spectroscopical properties which depend on the intensity of the incident radiation. They are relevant for a large amount of technical applications such as for photochromic materials, frequency conversion of lasers or photodynamic canter therapy. Structure-property relations for these properties are very complex and design of new materials in this field often needs support from computational chemistry.
Relativistic effects are effects originating from the theory of relativity. Most quantum chemical approaches neglect these effects as they render the working equations extremely complex while and their impact on the result is normally very small as long as only lighter element atoms are considered. As heavier atoms come into play, relativistic effects become more and more important it can no longer be neglected. The overall objective of the RelPro project was to provide a fast and reliable computational method which is able to calculate non-linear optical properties for molecular systems including heavy atoms using time-dependent density functional theory (TD-DFT).
During the RelPro project, the fundamental equations for these properties have been derived and a program has been written that is able to calculate first-order hyperpolarizabilities of heavy atom compounds in combination with other quantum chemistry programs.