scholarly journals On the accuracy of density functional theory and wave function methods for calculating vertical ionization energies

2015 ◽  
Vol 142 (19) ◽  
pp. 194114 ◽  
Author(s):  
Scott McKechnie ◽  
George H. Booth ◽  
Aron J. Cohen ◽  
Jacqueline M. Cole
Keyword(s):  
Density Functional Theory ◽  
Wave Function ◽  
Density Functional ◽  
Functional Theory ◽  
Ionization Energies ◽  
Vertical Ionization Energies

Density functional theory study of the vertical ionization energies of the valence and core electrons of cyclopentadiene, pyrrole, furan, and thiophene

2011 ◽  
Vol 89 (12) ◽  
pp. 1477-1488 ◽  
Author(s):  
Delano P. Chong
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Binding Energies ◽  
Test Cases ◽  
Absolute Deviation ◽  
Core Electron ◽  
Functional Theory ◽  
Ionization Energies ◽  
Benchmark Database ◽  
Vertical Ionization Energies

The procedure abbreviated as ΔPBE0(SAOP)/et-pVQZ, based on density functional theory, was developed recently for the calculation of vertical ionization energies of the valence electrons of organic and other small molecules and succeeded in giving results with an average absolute deviation of 0.21 eV from experiment for a collection of 115 reliable test cases of nonperhalo molecules. The objective of this work is to add a number of test cases to the benchmark database. We chose the set of molecules cyclo-C4H4X, with X = CH2, NH, O, and S, previously studied by many workers both experimentally and theoretically. The results show that the ΔPBE0(SAOP)/et-pVQZ procedure is not only as good as ab initio methods such as SAC-CI, OVGF, and ADC(3) in performance, but also handles inner valence ionized cations more efficiently. Although the core-electron binding energies of the titled molecules have not been as well investigated theoretically, we apply the methods we developed in recent years to calculate the binding energies of C1s, N1s, O1s, S1s, and S2p, which compare well with available experimental data.

Regaining the Woodward–Hoffmann rules for chelotropic reactions via conceptual DFT

2010 ◽  
Vol 88 (8) ◽  
pp. 858-865 ◽  
Author(s):  
Pablo Jaque ◽  
José V. Correa ◽  
Frank De Proft ◽  
Alejandro Toro-Labbé ◽  
Paul Geerlings
Keyword(s):  
Density Functional Theory ◽  
Wave Function ◽  
Density Functional ◽  
Pericyclic Reactions ◽  
Dual Descriptor ◽  
Conceptual Density Functional Theory ◽  
Functional Theory ◽  
Linear Path ◽  
Initial Hardness ◽  
Linear And Nonlinear

In our continuous effort to retrieve the Woodward–Hoffmann rules from conceptual density functional theory (DFT), we have examined the last type of pericyclic reactions, i.e., chelotropic reactions. Both the initial hardness response and the dual descriptor have been investigated to predict the allowed and forbidden character for the addition of SO2 to butadiene (4n system) and 1,3,5-hexatriene (4n + 2 system). It is shown that with both electronic descriptors, the conrotatory/disrotatory mode for the linear and nonlinear mechanisms are retrieved based on a density-only approach, free from consideration of orbital and (or) wave function symmetry. The dual descriptor moreover reveals that stabilizing interactions are presented only for the linear path, which can be considered as an overall favourable mechanism for a chelotropic reaction.

scholarly journals Separated-pair approximation and separated-pair pair-density functional theory

2016 ◽  
Vol 7 (3) ◽  
pp. 2399-2413 ◽  
Author(s):  
Samuel O. Odoh ◽  
Giovanni Li Manni ◽  
Rebecca K. Carlson ◽  
Donald G. Truhlar ◽  
Laura Gagliardi
Keyword(s):  
Density Functional Theory ◽  
Wave Function ◽  
Density Functional ◽  
Function Theory ◽  
Pair Approximation ◽  
Functional Theory ◽  
Complete Active Space ◽  
Pair Density ◽  
Comparable Accuracy ◽  
The Cost

Here we present the separated-pair approximation for wave function theory and show that it performs almost as well as the more demanding complete active space approximation. We show that the combination of an SP wave function with an on-top density functional yields comparable accuracy to CASPT2 at a small fraction of the cost.

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