Efficient Multi-Center Electron Repulsion Integrals for Exponential Type Orbitals: Two New Methods

Activity: Talk or presentation typesLecture and oral contribution

James Emil Avery - Lecturer

    Invited speaker

    The main obstacle to mainstream use of exponential type orbitals in quantum chemistry is the inefficiency of evaluating multi-centre inter-electron repulsion integrals. Recent years have seen excellent development towards overcoming this, but much improvement is still needed before we can treat ETOs as efficiently as Gaussian type orbitals. In this talk, I will present two new methods that yield very fast ERI evaluation for a special class of ETOs: Coulomb Sturmian orbitals. Coulomb Sturmians are a particularly useful class of exponential orbitals. They form a complete basis set, obey potential-weighted orthonormality relations, and their exponents can be automatically optimized to fit the problems under consideration. The talk will show that the most important integrals can be evaluated rapidly and accurately by means of the theory of hyperspherical harmonics. For the remaining many-center integrals, Coulomb Sturmians will be shown to have advantages over other ETO's because of their automatic scaling properties. Still greater speed can be achieved by splitting the integral evaluation into two parts: In an initial heavy precomputation step the large majority of the work is done. In this step, closed form expressions are generated for the integrals as functions of nuclear displacements. The integrals are broken up into small sums of products of radial and angular terms, and efficient code for evaluating the integrals is generated. Due to the automatic scaling of Sturmian orbitals, this step can be done once and for all; at runtime, integral evaluation as functions of nuclear displacements is measured in microseconds. The developed software will be added to the repository that is presented at this conference.
    12 Sep 2012

    Event (Conference)

    TitleMolecular Electronic Structure at Troy
    Abbreviated titleMEST 2012

    ID: 40958236