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Theory and Application Development of Electronic Structure Methods Involving Heavy Computation.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Theory and Application Development of Electronic Structure Methods Involving Heavy Computation./
Author:	Li, Run.
Description:	1 online resource (170 pages)
Notes:	Source: Dissertation Abstracts International, Volume: 79-02(E), Section: A.
Contained By:	Dissertation Abstracts International79-02A(E).
Subject:	Physical education. -
Online resource:	click for full text (PQDT)
ISBN:	9780355432626

Theory and Application Development of Electronic Structure Methods Involving Heavy Computation.
Li, Run.

Theory and Application Development of Electronic Structure Methods Involving Heavy Computation. - 1 online resource (170 pages)

Source: Dissertation Abstracts International, Volume: 79-02(E), Section: A.

Thesis (Ph.D.)--The University of North Dakota, 2017.

Includes bibliographical references

The propargyl radical, the most stable isomer of C3H3, is very important in combustion reactions. However, theoretical calculations have never been able to find a strong absorption around 242 nm as seen in experiments. In this study, we calculated the electronic energy levels of the propargyl radical using highly accurate multireference methods, including multireference configuration interaction singles and doubles method with triples and quadruples treated perturbatively [denoted as MRCISD(TQ)], as well as second and third order generalized Van Vleck perturbation theories (GVVPT2 and GVVPT3). Calculations indicate that this absorption can be solely attributed to a Franck-Condon-allowed transition from the ground B1 state to the Rydberg-like first A1 excited state. Calculations also show that GVVPT2 with a relatively small active space fails to capture enough Rydberg character of this excited state, while it can be recovered by GVVPT3, MRCISD, and MRCISD(TQ).

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2018

Mode of access: World Wide Web

ISBN: 9780355432626Subjects--Topical Terms:

1179721
Physical education.
Index Terms--Genre/Form:

554714
Electronic books.

Theory and Application Development of Electronic Structure Methods Involving Heavy Computation.
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100 1 $a Li, Run. $3 1194806
245 1 0 $a Theory and Application Development of Electronic Structure Methods Involving Heavy Computation.
264 0 $c 2017
300 $a 1 online resource (170 pages)
336 $a text $b txt $2 rdacontent
337 $a computer $b c $2 rdamedia
338 $a online resource $b cr $2 rdacarrier
500 $a Source: Dissertation Abstracts International, Volume: 79-02(E), Section: A.
500 $a Adviser: Mark R. Hoffmann.
502 $a Thesis (Ph.D.)--The University of North Dakota, 2017.
504 $a Includes bibliographical references
520 $a The propargyl radical, the most stable isomer of C3H3, is very important in combustion reactions. However, theoretical calculations have never been able to find a strong absorption around 242 nm as seen in experiments. In this study, we calculated the electronic energy levels of the propargyl radical using highly accurate multireference methods, including multireference configuration interaction singles and doubles method with triples and quadruples treated perturbatively [denoted as MRCISD(TQ)], as well as second and third order generalized Van Vleck perturbation theories (GVVPT2 and GVVPT3). Calculations indicate that this absorption can be solely attributed to a Franck-Condon-allowed transition from the ground B1 state to the Rydberg-like first A1 excited state. Calculations also show that GVVPT2 with a relatively small active space fails to capture enough Rydberg character of this excited state, while it can be recovered by GVVPT3, MRCISD, and MRCISD(TQ).
520 $a In order to speed up MRCISD(TQ) calculations, the triple and quadruple (TQ) perturbative corrections, the most time-consuming part of MRCISD(TQ) calculations, were parallelized using Message Passing Interface (MPI). The MRCISD(TQ) method is organized in the framework of macroconfigurations, which allows the use of incomplete reference spaces and provides an efficient means of screening large number of non-interacting configuration state functions (CSFs). The test calculations show that the parallel code achieved close to linear speed-up when the number of CSFs in each macroconfiguration is small. The speed-up suffers when large numbers of CSFs exist in only a few macroconfigurations.
520 $a The computer algorithm for second-order generalized van Vleck multireference perturbation theory (GVVPT2) was similarly parallelized using the MPI protocol, organized in the framework of macroconfigurations. The maximum number of CSFs per macroconfiguration is found to have less influence on the MPI speedup and scaling than in the case of MRCISD(TQ).
520 $a It was previously found that unrestricted local density approximation (LDA) orbitals can be used in place of MCSCF to provide orbitals for GVVPT2. This inspired us to use the more controllable restricted density functional theory (DFT) to provide unbiased orbitals for GVVPT2 calculations. In this study, the relationship between restricted DFT and unrestricted DFT were explored and the restricted DFT results were obtained by utilizing subroutines from unrestricted DFT calculations. We also found that the DIIS technique drastically sped up the convergence of RDFT calculations.
520 $a Plane wave DFT methods are commonly used to efficiently evaluate solid state materials. In this work, the electronic properties of pristine graphene and Zn-phthalocyanine tetrasulfonic acid (Zn-PcS) physisorbed on single-layer graphene were calculated using plane wave DFT. The Perdew-Burke-Ernzerhof functional with dispersion correction (PBE-D2) was used. The densities of states were obtained for both pristine and absorbed graphene, and the disappearance of the characteristic dip in the density of states of the adsorbed system was attributed to the lowest unoccupied molecular orbital of the adsorbed molecule. A small charge transfer from graphene to the molecule was found. We present comparison of DFT results with Scanning Tunneling Microscopy/Spectroscopy data.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2018
538 $a Mode of access: World Wide Web
650 4 $a Physical education. $3 1179721
655 7 $a Electronic books. $2 local $3 554714
690 $a 0523
710 2 $a ProQuest Information and Learning Co. $3 1178819
710 2 $a The University of North Dakota. $b Chemistry. $3 1194807
773 0 $t Dissertation Abstracts International $g 79-02A(E).
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10615199 $z click for full text (PQDT)