Web Release Date: January 18,
Toward the Exact Solution of the Electronic Schrödinger Equation for Noncovalent
Molecular Interactions: Worldwide Distributed Quantum Monte Carlo Calculations
and
Organisch-Chemisches Institut, Universität Münster, Corrensstrasse 40, D-48149 Münster, Germany and Institut für Physikalische Chemie, RWTH Aachen University, D-52056 Aachen, Germany
Received: September 20, 2007
In Final Form: December 10, 2007
Abstract:
Quantum Monte Carlo (QMC) calculations on the stacked (st) and Watson/Crick (wc) bound adenine/thymine (A/T) and cytosine/guanine (C/G) DNA base pair complexes were made possible with the first large scale distributed computing project in ab initio quantum chemistry, Quantum Monte Carlo at Home (QMC@HOME). The results for the interaction energies (wc-A/T = 15.7 kcal/mol, wc-C/G = 30.2 kcal/mol, st-A/T = 13.1 kcal/mol, st-C/G = 19.6 kcal/mol) are in very good agreement with the best known coupled-cluster based estimates. The accuracy of these values is further supported by calculations on the S22 benchmark set of noncovalently bound systems, for which we obtain a small mean absolute deviation of 0.68 kcal/mol. Our results support previous claims that the stacking energies are of comparable magnitude to the interactions of the commonly discussed hydrogen-bonded motif. Furthermore, we show that QMC can serve as an advantageous alternative to conventional wave function methods for large noncovalently bound systems. We also investigated in detail all technical parameters of the QMC simulations and recommend a careful optimization procedure of the Jastrow correlation factors in order to obtain numerically stable and reliable results.
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