STRUCTURE AND STABILITY OF MOLECULAR CARBON - IMPORTANCE OF ELECTRON CORRELATION

The electronic structure of medium-size molecular carbon is determined by a variety of methods, including density functional, quantum chemistry, and quantum Monte Carlo approaches. We demonstrate (i) significant differences between the mean-field methods in determining the minimum energy structure of a set of C-10 and C-20 isomers, and (ii) the crucial importance of an accurate account of electron correlation which enables us to predict, e.g., that of the available geometries for C-20 the relaxed graphite fragment (bowl) is lower in energy than either the ring or fullerene isomers.