mcci

A Monte-Carlo configuration generation computer program for the calculation of electronic states of atoms, molecules, and quantum dots. Nature of problem: The mcci program is a configuration interaction program and is suitable for generating highly accurate solutions to quantum-many body problems; there is no inherent limit set on the number of fermions, but typical calculations to date have considered molecules with up to 20 correlated electrons. With reasonable sized basis set expansions, 99 per cent of the correlation energy has been obtained for small molecular systems. In principle, there is no limit to the accuracy of the calculations outside of memory and CPU time constraints. Selective convergence on excited states is possible with the program. The program calculates energy matrix elements from one- and two-body integrals, which are read-in externally. The program is independent of the operators used in these expectation values, and hence is equally valid for any spin independent Hamiltonian composed of one- and two-body operators. Accurate calculations of atomic and molecular spectra have been demonstrated with the program. Calculation of the spectra of point defects in solids is currently being investigated, and the electronic states for simplified models of quantum dots are also being studied with use of the program for electronic applications. Treatment of spin states is exact within the program allowing for calculation of simultaneous eigenfunctions of the energy H^ and spin S^z, S^**2 operators.