An orthogonal approach to determine extremely localised molecular orbitals

The introduction of extremely localised molecular orbitals, a current issue in modern physical chemistry, justifies chemical intuition and provides a useful tool towards the description of large molecules. In this paper, a possible strategy to determine these orbitals is proposed. The algorithm implemented has been tested by effecting computations on water, ammonia, benzene and naphthalene by employing different intramolecular partitionings. Ethane and biphenyl have been considered for application of the algorithm to the study of rotational barriers. Our scheme also includes the possibility to compute derivatives with respect to nuclear coordinates.