ITLApplied  Computational Mathematics Division
ACMD Seminar Series
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Hylleraas-CI Calculations on the Beryllium Atom: A Progress Report

Stanley A. Hagstrom
Indiana University, Department of Chemistry

Tuesday, January 24, 2006 15:00-16:00,
NIST North (820), Room 145
Tuesday, January 24, 2006 13:00-14:00,
Room 4550

Abstract: Few-body atomic and molecular systems, such as He, Li, Be, H2+, and H2, are important to our understanding of the microscopic world and, accordingly, have received increasing attention in recent years as computing power has increased. In this talk I review recent results on small atoms. Emphasis will be on the Hylleraas-Configuration Interaction (Hy-CI) method, introduced by Sims and Hagstrom in the early 1970s, and its close connection to the more familiar Hylleraas methods. In particular, a large-scale non-relativistic Hy-CI calculation currently under way on the ground state of the Beryllium atom (Be) will be described and preliminary results presented. This work is being carried out together with Dr. James Sims of NIST. Although structurally simple, these two-, three-, and four-body systems are, however, intrinsically complex and present a number of interesting challenges from a computational standpoint. The need for high numerical accuracy (30 digit), massive numbers of complicated integrals to be computed, complex analytic expressions for building Hamiltonian matrix elements, as well as the need to efficiently solve a very large-scale generalized eigenvalue problem, will be discussed. In this connection, a new implementation of the Inverse Iteration method for the generalized real symmetric positive definite eigenvalue problem (GRSPDEVP) should be of interest. This code has been specifically tailored to meet the rather specialized needs of the few-body problem. Time permitting, our parallelization of selected aspects of this work will be described.

Speaker Bio: Stanley Hagstrom received his PhD in Chemical Physics from Iowa State University. He is currently Emeritus Professor of Chemistry and Computer Science at Indiana University, which he joined in 1957. Prof. Hagstrom's research interests include ab initio quantum chemistry with a focus on the accurate theoretical treatment of small atoms and molecules. In this regard, he has special interest in the few-body problem, the Slater molecular integrals problem, large-scale eigenvalue problems, and associated computer methodologies. He has done extensive consulting in the area of theoretical spectroscopy of diatomic molecules and the thermal properties of high temperature air. Prof. Hagstrom is one of the founders of Indiana University's Department of Computer Science as well as its Quantum Chemistry Program Exchange.

Contact: J. S. Sims

Note: Visitors from outside NIST must contact Robin Bickel; (301) 975-3668; at least 24 hours in advance.

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