Speaker : | Jozef Noga Institute of Inorganic Chemistry Slovak Academy of Sciences, Bratislava and Department of Physical and Theoretical Chemistry Faculty of Science, Comenius University, Bratislava |

Topic : | Towards
high precision calculations of molecular energies and properties via explicitly correlated coupled cluster theory |

Date : | January 14, 2007 |

Time : | 11.15 AM |

Venue : | C V Raman Hall, IACS |

All are cordially invited to attend.

**Abstract: **One of the major difficulties with ab initio quantum chemical
calculations based on the expansion of the wave function in terms of the one-particle
basis is hidden in the fact that with inclusion of higher and higher angular
momenta such expansions converge very slowly to the exact limits. The slow convergence
is related to a wrong description of the wave function for coalescence of two
electrons, known as dynamical electron correlation. This defect can be eliminated
by an explicit incorporation of the interelectronic coordinate into the wave
function expansion. R12/F12 theories for treating the dynamical electron correlation
are discussed, and, in particular the explicitly correlated R12/F12 coupled
cluster theory is introduced and its performance in different fields of chemical
interest is shown.