# Theoretical chemistry

Using quantum-chemical methods, chemical systems are studied theoretically, by calculating quantum-mechanical wave functions on computers. A central activity of the section’s work is the development of new computational techniques for the study of molecular and solid-state systems, rigorously based on the laws of quantum mechanics.

## About the group

### Permanent scientific staff

Associate Professor Michele Cascella

Associate Professor Thomas Bondo Pedersen

Senior Engineer Simen Sommerfelt Reine

## Centre of Excellence

The group is a part of the research centre CTCC.

## Section seminars:

Different topics will be presented, reflecting the research interests of our group. Currently, the seminars are held in room V205.

## Quantum chemistry at the Department of Chemistry

Using quantum-chemical methods, chemical systems are studied theoretically, by calculating quantum-mechanical wave functions on computers. A central activity of the group’s work is the development of new computational techniques for the study of molecular and solid-state systems, rigorously based on the laws of quantum mechanics.

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Chemical systems, atoms and molecules, abide the laws of quantum mechanics. These laws were developed between 1925 and 1928, as a reaction to discrepancies between experiments and the laws of classical mechanics.

Today, computers are used to solve quantum chemical problems, and within the field of chemistry more than 20% of all published articles uses quantum mechanical calculations. This percentage is increasing by about 1% per year.

### What do we do?

Most people working with quantum chemistry participate in the development of the software-package DALTON, which is based on an international project (mainly in Scandinavia). More than a thousand research-institutions and universities all over the world use the code, consisting of an excess of 700 000 lines. DALTON is thereby one of the most wide spread quantum chemical software tools available.

Testing the code on real problems is an important and time-consuming part of our development. We here prefer to collaborate with people with expertise in different areas of research. If you have suggestions for such collaborations we'll be happy to hear from you.

Starting from the Schrödinger-equation, ab initio quantum mechanical tools to study molecules are created (ab initio means from scratch). Such ab initio tools can be compared to the functions of a calculator. The calculator can with some experience be used to calculate chemical properties.

Based on the Schrödinger-equation a detailed description of chemical systems can be obtained, and for small systems (up to about 10 atoms) highly accurate calculations can be performed. The accuracy in such calculations on small systems have in many cases proven more accurate than current experimental results.

To obtain similar accuracy for large systems, the cost of the calculations has to be reduced and our current developments go in this direction. DALTON has allready been used to calculate properties of molecules consisting of more than 1 000 atoms, and in a few years we expect this limit to be above 10 000 atoms.

Published Nov 29, 2010 03:33 PM - Last modified May 25, 2012 02:22 PM