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 po ssible strategy to determine these orbitals is proposed. The algorithm impl emented has been tested by effecting computations on water. ammonia, benzen e and naphthalene by employing different intramolecular partitionings. Etha ne and biphenyl have been considered for application of the algorithm to th e study of rotational barriers. Our scheme also includes the possibility to compute derivatives with respect to nuclear coordinates.