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The core ionization energies of the second-period and third-period elements are studied by ΔSCF and Slater's transition state (STS) theory by using Hartree–Fock (HF) and Kohn–Sham (KS) approximations. Electron correlation increases the estimated core ionization energies, while the self-interaction error (SIE) decreases them, especially for the third-period elements and is a more significant factor. As a result, while HF lacks electron correlation, it is free of SIE and reasonably predicts the core ionization energies. The core ionization energies calculated by HF STS are very close to those calculated by HF ΔSCF, showing that STS reasonably describes the relaxation of the core hole. The core ionization energies calculated by KS are particularly sensitive to the SIE of the functional used, with functionals having less SIE yielding more accurate ΔSCF core ionization energies. Consequently, BH&HLYP gives better results than B3LYP and LC-BOP since BH&HLYP is the hybrid functional with high proportion of the exact HF exchange. Although the core ionization energies are underestimated by ΔSCF due to SIE, STS gives larger core ionization energies than ΔSCF due to a concave behavior of the error curves of STS, which is also related to SIE. The mean absolute deviations of STS relative to ΔSCF, and relative to the experiment, are almost constant regardless of the nuclei among the element in the second period, and likewise among those in the third period. The systematic nature suggests that shifting the STS core ionization energies may be useful. We propose the shifted STS (1) for reproducing ΔSCF values, and the shifted STS (2) to reproduce the observed ones for KS calculations. Both schemes work quite well. The calculated results of KS ΔSCF and STS vary depending on the functional. However, the variation of each species' shifted STS (2) is very small, and all shifted STS (2) values are close to the observed ones. As the shifted STS require only one SCF calculation, they are simple and practical for predicting the core ionization energies. [ABSTRACT FROM AUTHOR]

We generalize Slater's transition state concept by deriving systematic higher-order transition state approximations. Numerical validation is performed by the calculation of transition energies for various excitations, including core, valence, and charge-transfer excitations, at Hartree–Fock and Kohn–Sham density functional theory levels. All higher-order transition state approximations introduced in this study accurately reproduce the results from delta self-consistent-field calculations. In particular, we demonstrate that the third-order generalized transition state (GTS3) approximation is a promising alternative to the original, owing to a good balance between the accuracy and computational cost. We also demonstrate that accurate and reliable results can be obtained with a low computational cost by combining the GTS3 approximation with the transition potential scheme. [ABSTRACT FROM AUTHOR]

The core ionization energies of second‐ and third‐period elements of the molecules C2H5NO2, SiF4, Si(CH3)4, PF3, POF3, PSF3, CS2, OCS, SO2, SO2F2, CH3Cl, CFCl3, SF5Cl, and Cl3PS are calculated by using Hartree‐Fock (HF), and Kohn‐Sham (KS) with BH&HLYP, B3LYP, and LC‐BOP functionals. We used ΔSCF, Slater's transition state (STS), and two previously proposed shifted STS (1) and shifted STS (2) methods, which have been developed. The errors of ΔSCF and STS come mainly from the self‐interaction errors (SIE) and can be corrected with a shifting scheme. In this study, we used the shifting parameters determined for each atom. The shifted STS (1) reproduces ΔSCF almost perfectly with mean absolute deviations (MAD) of 0.02 eV. While ΔSCF and STS vary significantly depending on the functional used, the variation of shifted STS (2) is small, and all shifted STS (2) values are close to the observed ones. The deviations of the shifted STS (2) from the experiment are 0.24 eV (BH&HLYP), 0.19 eV (B3LYP), and 0.23 eV (LC‐BOP). These results further support the use of shifted STS methods for predicting the core ionization energies. [ABSTRACT FROM AUTHOR]

We have extended Slater's transition state concept for the approximation of the difference in total energies of the initial and final states by three orbital energies of initial, final, and half-way Slater's transition states of the system. Numerical validation was performed with the ionization energies for H2O, CO, and pyrrole by calculation using Hartree–Fock (HF) and Kohn–Sham (KS) theories with the B3LYP and LCgau-core-BOP functionals. The present extended method reproduces full ΔSCF very accurately for all occupied orbitals obtained with HF and for valence orbitals obtained with KS. KS core orbitals have some errors due to the self-interaction errors, but the present method significantly improves the core electron binding energies. In its current form, the newly derived theory may not yet be practically useful, but it is simple and conceptually useful for gaining improved understanding of SCF-type orbital theories. [ABSTRACT FROM AUTHOR]

Several different types of density functional theory (DFT) exchange correlation functionals were applied to a periodic boundary condition (PBC) system [carbon monoxide (CO) adsorbed on Cu(111): CO/Cu(111)] and the differences in the results calculated using these functionals were compared. The exchange correlation functionals compared were those of Perdew–Burke–Ernzerhof (PBE) and those of long-range corrected density functional theory (LC-DFT), such as LC-ωPBE(2Gau) and LC-BLYP(2Gau). Solid state properties such as the partial density of states were calculated in order to elucidate the detailed adsorption mechanisms and back-bonding peculiar to the CO/Cu(111) system. In addition, our benchmark analysis of the correlations among the orbitals of CO and Cu metal using LC-DFT reasonably was in line with the experimentally observed adsorption site. The computation time was reasonable, and other numerical results were found to agree well with the experimental results and also with the theoretical results of other researchers. This suggests that the long-range Hartree–Fock exchange integral should be included to correctly predict the electronic nature of PBC systems. [ABSTRACT FROM AUTHOR]

The redox switching of doped 1,5‐azulenequinones/hydroquinones wired between gold electrodes is investigated using density functional theory and the nonequilibrium Green's function. Their electronic transport properties when separately doped with nitrogen and boron as well as co‐doping of these atoms are examined. The results illustrate a significant enhancement of the current at low bias voltage in some of the 12 doped studied systems, leading to "switching on" the transmission, where the greatest switching ratio is 18. These systems also exhibit a modest rectification in which the greatest rectification ratio is 4. The significance of the position of the doped atom and the functional group on the switching behavior is analyzed through the transmission spectra and molecular orbitals. The present study broadens knowledge of organic redox switching bringing in potential diverse options for future molecular electronic circuit components. [ABSTRACT FROM AUTHOR]

Recently, we proposed a simple yet efficient method for the computation of a long‐range corrected (LC) hybrid scheme [LC‐DFT(2Gau)], which uses a modified two‐Gaussian attenuating operator instead of the error function for the long‐range HF exchange integral. This method dramatically reduced the computational time while maintaining the improved features of the LC density functional theory (DFT). Here, we combined an LC hybrid scheme using a two‐Gaussian attenuating operator with one‐parameter progressive correlation functional and Becke88 exchange functional with varying range‐separation parameter values [LC‐BOP(2Gau) with various μ values of 0.16, 0.2, 0.25, 0.3, 0.35, 0.4, and 0.42] and demonstrated that LC‐BOP(2Gau) reproduces well the thermochemical and frontier orbital energies of LC‐BOP. Additionally, we revised the scaling factors of the Gaussian multipole screening scheme for LC‐DFT(2Gau) to correspond to the angular momentum of orbitals, which decreased the energy deviations from the energy with the no‐screening scheme. © 2018 Wiley Periodicals, Inc. The authors proposed a simple yet efficient method for the computation of a long‐range corrected (LC) hybrid scheme [LC‐DFT(2Gau)], which uses a modified two‐Gaussian attenuating operator instead of the error function for the long‐range HF exchange integral. This method dramatically reduced the computational time while maintaining the improved features of the LC density functional theory. The authors combined an LC scheme using a two‐Gaussian attenuating operator with OP correlation functional and Becke88 exchange functional with varying range‐separation parameter values [LC‐BOP(2Gau) with μ = 0.16–0.42] and demonstrated that LC‐BOP(2Gau) reproduces well the thermochemical and frontier orbital energies of LC‐BOP. [ABSTRACT FROM AUTHOR]

In the present study, we have reparametrized the HISS exchange functional. The new "reHISS" exchange provides a balance between short‐ and mid‐range Hartree–Fock exchange (HFX) and a large total HFX coverage, with a fast convergence to zero HFX in the long range. The five parameters in this functional (according to equations 3 and 4 in the main text) are cSR = 0.15, cMR = 2.5279, cLR = 0, ωSR = 0.27, and ωLR = 0.2192. The combination of reHISS exchange with a reparametrized B97c‐type correlation functional (Chan et al., J. Comput. Chem. 2017, 38, 2307) and a D2 dispersion term (s6 = 0.6) gives the reHISSB‐D method. We find it to be more accurate than related screened‐exchange methods and, importantly, its accuracy is more uniform across different properties. Fundamentally, our analysis suggests that the good performance of the reHISS exchange is related to it capturing a near‐optimal proportion of HFX in the range of interelectronic distance that is important for many chemical properties, and we propose this range to be approximately 1–4Å. © 2018 Wiley Periodicals, Inc. Three‐range screened‐exchange density functional theory (SX‐DFT) protocol provides an opportunity for attaining superior accuracy when compared with two‐range SX‐DFT. The present study has established the optimal variations for mixing Hartree–Fock and DFT components. The authors have harnessed this knowledge to devise the reHISSB‐D method. It has improved accuracy when compared with related SX‐DFT methods, and provides a solid foundation for further refinement of SX‐DFT. [ABSTRACT FROM AUTHOR]