The present-day version of the Consistent Force Field, CFF, was developed at Department of Chemistry of the Technical University of Denmark, based on the original work of Lifson, Levitt and Warshel at Chemical Physics Department of the Weizmann Institute of Science in Israel during the late 1960es.

The CFF belongs to the group of methods called molecular mechanics where the potential energy of a molecule, a molecular complex or a crystal is calculated as a sum of inter-atomic potentials, whose parameters are ideally obtained by optimization on experimental structural and spectroscopic data for the pure substances. A set of parameters is called a force field.

It is a tool with which you can develop force fields, in the sense that you can optimize the parameters of potential energy functions on several categories of data for molecules in gaseous and crystalline states.

The imbedded methods allow for calculation of molecular properties such as conformations, vibrational frequencies and thermodynamic functions. The integrated optimisation facility is unique and fundamental to the CFF concept.

The most important technical contributions from the Danish group are: weighted Levenberg-Marquardt optimization, a crystal simulator using Ewald sums and an interactive graphical interface to the optimization algorithm GOPT (Graphics OPtimization Tool).

The uniqueness of CFF is found in its optimization capabilities. At present CFF can optimize on bond lengths, valence angles, torsional angles, out-of-plane angles, non-bonded distances, unit cell dimensions, lattice energies, molecular potential energies, dipole moments, and vibrational frequencies.

Force fields based on theoretical data obtained from large-scale ab initio calculations at the MP2 level or employing DFT to include electron correlation are currently being optimised.

Applications of CFF are numerous: coordination compounds; saccharides; aluminosilicates; intermolecular interactions and phase equilibria.

Selected general references

On special occasions, and if schedules permit, a lecture of an historical character can be offered.

A lecture in Danish on former and current principles of molecular modelling was given in April 2004 at Roskilde University. The text, with illustrations, is available. Right-click to open the .pdf file. This lecture, and others, may also be found via the Model Day homepage

Course related to CFF .

A Ph. D. course aiming specifically at force field development through optimisation of potential energy function parameters has been developed :  Force Field Development for Molecular Modelling.

Both courses will be renewed from time to time.

Dr. techn. Kjeld Rasmussen, R, Reader (retired)
Photo is from July 2004.

This is from June 2004, 50 years after I donned my student's cap.
Photos from the 50 y festivities are decidedly for the old boys and girls,
and are not of interest to others.

Telephone: + 45 39 69 18 13
Curriculum Vitae: short; complete; complete in Danish
List of publications: shortened; complete


On 31 July, 2003, by the end of the month in which I became 67 years old, I had to retire. As a farewell, I gave a seminar recounting more than 35 years of work in the Institute in Danish. I translated it into English for the benefit of those who are not so proficient in Danish.

Hobbies :
My wife Birgit and I enjoy Folkdance; Danish and traditional American.
We also are rodeo afficionados and have attended several rodeos in Arkansas and Colorado.

Creativity, divine and humane

Fornyet 20-10-2004