Please use this identifier to cite or link to this item:
http://hdl.handle.net/11375/24133
Title: | Systematic improvement of approximations with smooth models of the Coulomb potential |
Authors: | Gonzalez Espinoza, Cristina Elizabeth |
Advisor: | Ayers, Paul W. Savin, Andreas |
Department: | Chemistry and Chemical Biology |
Keywords: | Model potential;Method development;Range separation;Energy extrapolation |
Publication Date: | 2018 |
Abstract: | Orbital-based methods for electronic-structure calculations are limited to atoms or molecules with up to about 50 electrons. This limitation comes from the requirement of a long expansion in basis functions to approximate correctly the wave function. Replacing the Coulomb interaction with a smooth model potential has two main consequences: first, the wave function becomes cuspless and the expansion in basis functions converges more rapidly, and second, the smooth potential describes a weaker interaction at the electronic coalescence point, which leads to the loss of accuracy. This work explores whether one can construct models with smooth, non-singular, potentials, but without compromising accuracy. The key idea is to use extrapolation procedures to predict the energy for the Coulomb interaction from a sequence of (cheaper) calculations for smooth potentials. By replacing the Coulomb electron-electron interaction with a smooth potential, using the semi-stochastic heat-bath configuration interaction method (SHCI) to select key configurations, and extrapolating to the limiting (non-smoothed) Coulomb potential, we were able to retain the accuracy of full configuration interaction (FCI) calculations, at reduced computational cost. |
URI: | http://hdl.handle.net/11375/24133 |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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thesis.pdf | 3.94 MB | Adobe PDF | View/Open |
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