Simple and accurate scheme to compute electrostatic interaction : Zerodipole summation technique for molecular system and application to bulk water
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Abstract
The zerodipole summation method was extended to general molecular systems, and then applied to molecular dynamics simulations of an isotropic water system. In our previous paper [I. Fukuda, Y. Yonezawa, and H. Nakamura, J. Chem. Phys.134, 164107 (2011)10.1063/1.3582791], for evaluating the electrostatic energy of a classical particle system, we proposed the zerodipole summation method, which conceptually prevents the nonzerocharge and nonzerodipole states artificially generated by a simple cutoff truncation. Here, we consider the application of this scheme to molecular systems, as well as some fundamental aspects of general cutoff truncation protocols. Introducing an idea to harmonize the bonding interactions and the electrostatic interactions in the scheme, we develop a specific algorithm. As in the previous study, the resulting energy formula is represented by a simple pairwise function sum, enabling facile applications to highperformance computation. The accuracy of the electrostatic energies calculated by the zerodipole summation method with the atombased cutoff was numerically investigated, by comparison with those generated by the Ewald method. We obtained an electrostatic energy error of less than 0.01% at a cutoff length longer than 13 Å for a TIP3P isotropic water system, and the errors were quite small, as compared to those obtained by conventional truncation methods. The static property and the stability in an MD simulation were also satisfactory. In addition, the dielectric constants and the distancedependent Kirkwood factors were measured, and their coincidences with those calculated by the particle mesh Ewald method were confirmed, although such coincidences are not easily attained by truncation methods. We found that the zero dampingfactor gave the best results in a practical cutoff distance region. In fact, in contrast to the zerocharge scheme, the damping effect was insensitive in the zerocharge and zerodipole scheme, in the molecular system we treated. We discussed the origin of this difference between the two schemes and the dependence of this fact on the physical system. The use of the zero dampingfactor will enhance the efficiency of practical computations, since the complementary error function is not employed. In addition, utilizing the zero dampingfactor provides freedom from the parameter choice, which is not trivial in the zerocharge scheme, and eliminates the error function term, which corresponds to the timeconsuming Fourier part under the periodic boundary conditions.
The following article appeared in J. Chem. Phys. 137, 054314 (2012) and may be found at http://scitation.aip.org/content/aip/journal/jcp/137/5/10.1063/1.4739789
Journal

 The Journal of Chemical Physics

The Journal of Chemical Physics (137), 054314, 2012
AIP Publishing