Dispersion Energy in Density-functional Theory

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" Dispersion Energy in Density-functional Theory "
Shahbaz, Muhammad Szalewicz, Krzysztof

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1051112
Doc. No	:	TL50229
Main Entry	:	Shahbaz, Muhammad
Title & Author	:	Dispersion Energy in Density-functional Theory\ Shahbaz, MuhammadSzalewicz, Krzysztof
College	:	University of Delaware
Date	:	2019
Degree	:	Ph.D.
student score	:	2019
Note	:	181 p.
Abstract	:	Density Functional Theory (DFT), in various local and semilocal approximations, cannot completely describe long-range correlations between the electrons responsible for dispersion interactions. A large number of methods have been designed to correct DFT for the missing dispersion effects (DFT+D methods). These methods add a fraction of true dispersion energy to DFT methods assuming that a part of it has already been recovered by DFT. We estimate the amount of dispersion recovered by different popular DFT methods and show that what appears to be recovered dispersion energy does not possess the physical character expected of dispersion interactions. Moreover, a large part of it originates from those terms of the DFT interaction energy that do not have any physical mechanism to capture such effects. The technique used to estimate the recovered dispersion will help for future developments of DFT methods as it points out the shortcomings of the dispersionless parts of the DFT interaction energy as well. A new method for calculating dispersion interactions is also developed using a modified polarizability density from nonlocal correlation methods. The performance of the new method is tested on a set of dimers at various intermonomer separations. The new method outperforms all nonlocal correlation functionals and reduces the average error on the test set by at least a factor of 2. Finally, a path for the future development of nonlocal correlation methods is provided by comparing polarizability densities from nonlocal correlation functionals to the accurate one provided by time-dependent DFT.
Descriptor	:	Physics
Added Entry	:	Szalewicz, Krzysztof
Added Entry	:	University of Delaware