A local projection method for the linear combination of atomic orbital implementation of density‐functional theory

1991 ◽  
Vol 94 (2) ◽  
pp. 1208-1214 ◽  
Author(s):  
Weitao Yang
Keyword(s):  
Density Functional Theory ◽  
Linear Combination ◽  
Projection Method ◽  
Density Functional ◽  
Atomic Orbital ◽  
Functional Theory ◽  
Local Projection

scholarly journals Structural and spectroscopic characterization and DFT studies of 2-amino-1,10-phenanthrolin-1-ium chloride

2019 ◽  
Vol 10 (2) ◽  
pp. 95-101
Author(s):  
Sebile Işık Büyükekşi ◽  
Namık Özdemir ◽  
Abdurrahman Şengül
Keyword(s):  
Density Functional Theory ◽  
Electronic Absorption ◽  
13C Nmr ◽  
Density Functional ◽  
Electronic Absorption Spectra ◽  
Chemical Shifts ◽  
Atomic Orbital ◽  
Basis Set ◽  
Functional Theory ◽  
1H And 13C Nmr

A versatile synthetic building block, 2-amino-1,10-phenanthrolin-1-ium chloride (L∙HCl) was synthesized and characterized by IR, 1H and 13C NMR DEPT analysis, UV/Vis and single-crystal X-ray diffraction technique. The molecular geometry, vibrational wavenumbers and gauge including atomic orbital (GIAO), 1H and 13C NMR chemical shifts values of the title compound in the ground state were obtained by using density functional theory (DFT/B3LYP) method with 6-311++G(d,p) basis set and compared with the experimental data. Electronic absorption spectrum of the salt was determined using the time-dependent density functional theory (TD-DFT) method at the same level. In the NMR and electronic absorption spectra calculations, the effect of solvent on the theoretical parameters was included using the default model with DMSO as solvent. The obtained theoretical parameters agree well with the experimental findings.

scholarly journals Structural Stability and Thermodynamic Properties of (Y2O3)n(n=1-15) Clusters Based on Density Functional Theory

2021 ◽  
Author(s):  
Xin Jiang ◽  
Zhenming Zhang ◽  
Diqiang Luo ◽  
Jinglin You ◽  
Chaobin Lai
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Yttrium Oxide ◽  
Density Functional ◽  
Atomic Orbital ◽  
Cluster Structure ◽  
Functional Theory ◽  
Average Binding Energy ◽  
Bee Colony ◽  
Different Temperatures

The initial configuration of Yttrium oxide clusters (Y2O3)n(n=1-15) was creatively constructed by combining artificial bee colony algorithm with density functional theory. The structures of large and medium-sized yttrium oxide clusters with molecular number greater than 10 were established for the first time, and many new structures that are different from existing research have been obtained. The average binding energy, second-order difference energy, HOMO-LUMO gap, density of states and other properties of the clusters were analyzed. The thermodynamic properties and behavior of nano yttrium oxide clusters at different temperatures and sizes were discussed. Studies have shown that for small-sized clusters, the atomic stacking structure is cage-like, while for medium-sized and large-sized clusters, the composite trapezoidal structure and ellipsoid-like structure are more stable. The nanoclusters tend to be stable as a whole, and the relative stability of the cluster structure is higher when n = 2,4,7,9. The effect of yttrium oxygen atomic orbital on bonding is analyzed. The heat capacity (Cp), enthalpy change (H) and entropy (S) of (Y2O3)n (n=1-15) clusters increase with the increase of temperature (T), and the vibration free energy (Gv) decreases with the increase of T. The stability of the clusters changes in the temperature range of 300K-500K.

Density Functional Theory Based Modeling of the Corrosion on Iron Surfaces

2013 ◽  
Vol 58 (2) ◽  
pp. 321-323 ◽  
Author(s):  
N. Nunomura ◽  
S. Sunada
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Atomic Orbital ◽  
Atomic Layer ◽  
Iron Surface ◽  
Basis Set ◽  
Water Molecules ◽  
Aqueous Corrosion ◽  
Functional Theory ◽  
Adsorption Of Water

In order to understand the first steps of the aqueous corrosion of iron, we have performed density functional theory (DFT) based calculations for water molecules and pre-covered oxygen on iron surface. The surface structure is modeled by iron atomic layer and vacuum region, and then oxygen atom and water molecules are displaced on the surface. Self consistent DFT calculations were performed using a numerical atomic orbital basis set and a norm-conserve pseudopotential method. According to our calculations, with increasing surface oxygen coverage, the iron surface is found to be not activated, which leads to a feeble adsorption of water molecules on iron surface. Our results show that the surface covered oxygen exerts an influence on the adsorption of water molecules on iron surface.

scholarly journals Graphite as A Hydrogen Storage in Fuel Cell System: Computational Material Study for Renewable Energy

2017 ◽  
Vol 17 (2) ◽  
pp. 103
Author(s):  
Rahmat Gunawan ◽  
Cynthia Linaya Radiman ◽  
Muhamad Abdulkadir Martoprawiro ◽  
Hermawan K. Dipojono
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Storage ◽  
Density Functional ◽  
Alkali Metals ◽  
Correlation Energy ◽  
Atomic Orbital ◽  
Hydrogen Gas ◽  
Basis Set ◽  
Functional Theory ◽  
Orbital Contribution

The Hydrogen storage based-graphite materials have been investigated theoretically via Density Functional Theory (DFT) approach. The native graphite was compared to the modified graphite, namely the intercalation graphite (GICs, graphite intercalated compounds). Here the GICs was intercalated by alkali metals (Li, Na and K). The electronic structures, energetics and atomic orbital contributions of hydrogen-graphite system, GICs, and hydrogen-GICs were studied by calculation approach of gradient corrected PBE (Perdew-Burke-Ernzerhof) for recovery of exchange-correlation energy. The calculation was supported by using basis set of the plane waves whereas the computation of electron-core by using Ultrasoft Vanderbilt pseudopotential. The computational calculation provides four main studies i.e. molecular geometry relaxation, determination of electronic bands structure of energy, energy state density (DOS) and atomic orbital contribution by charge density differences.Keywords: Density Functional Theory, hydrogen gas, graphite intercalated material

Systematic Gauge-Including Atomic Orbital-Hybrid Density Functional Theory Linear Regressions for 13C NMR Chemical Shifts Calculation

2020 ◽  
Vol 12 (3) ◽  
pp. 364-370
Author(s):  
Sara Sâmitha Souza ◽  
Mariana Aparecida de Souza Martins ◽  
Antonio Maia de Jesus Chaves Neto ◽  
Gunar Vingre Da Silva Mota ◽  
Fabio Luiz Paranhos Costa
Keyword(s):  
Density Functional Theory ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Density Functional ◽  
Chemical Shifts ◽  
Atomic Orbital ◽  
Basis Set ◽  
Functional Theory ◽  
Linear Regressions ◽  
Nuclear Magnetic

Density-functional theory calculations of the magnetic shielding for nuclear magnetic resonance provide an important contribution to understand the experimental values obtained in laboratory for chemical shifts present in the samples. From of a comparative of the performance of ten hybrid functional within of the framework of the density-functional theory using 10 different hybrid functionals with 3-21G (B1), 6-31G(d) (B2) and 6-31+ G(d, p) (B3) basis set, with intuit of evaluating of performance of the 13 C nuclear magnetic resonance from a representative of the terpene class and a heterocyclic compound, (–)-loliolide ((7aR)-6-hydroxy-4,4,7a-trimethyl-6,7-dihydro-5H1-benzofuran-2-one). This molecule, satisfactorily, represents the main structure of this class, with conformational freedom, optical activity and a benzofuran nucleus. The ωB97X-D, MPW1K and HSEH1PBE functionals presented the best calculation performance. It is interesting to note that after the use of linear regressions all root mean square error values for ωB97X-D were lower than 3 ppm. These are 2.91 ppm (B1), 2.46 (B2) ppm and 2.62 ppm (B3). The information contained in this work can be used for the assignment of experimental nuclear magnetic resonance spectra and will motivate further studies involving the theoretical calculation of the chemical shift of 13C.

Investigation of electron density changes at the onset of a chemical reaction using the state-specific dual descriptor from conceptual density functional theory

2015 ◽  
Vol 17 (14) ◽  
pp. 9359-9368 ◽  
Author(s):  
Frank De Proft ◽  
Valérian Forquet ◽  
Benjamin Ourri ◽  
Henry Chermette ◽  
Paul Geerlings ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Transition State ◽  
Linear Combination ◽  
Electron Density ◽  
Chemical Reaction ◽  
Density Functional ◽  
The State ◽  
Dual Descriptor ◽  
Conceptual Density Functional Theory ◽  
Functional Theory

The electron density changes from reactants towards the transition state of a chemical reaction is expressed as a linear combination of the state-specific dual descriptors (SSDD) of the corresponding reactant complexes.

scholarly journals Density Functional Theory Study on Conformers of Benzoylcholine Chloride

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Mustafa Karakaya ◽  
Fatih Ucun ◽  
Ahmet Tokatlı
Keyword(s):  
Density Functional Theory ◽  
Ground State ◽  
Density Functional ◽  
Atomic Orbital ◽  
Nbo Analysis ◽  
Vibrational Frequencies ◽  
Molecular Structures ◽  
Basis Set ◽  
Functional Theory ◽  
B3lyp Method

The optimized molecular structures and vibrational frequencies and also gauge including atomic orbital (GIAO)1H and13C NMR shift values of benzoylcholine chloride [(2-benzoyloxyethyl) trimethyl ammonium chloride] have been calculated using density functional theory (B3LYP) method with 6-31++G(d) basis set. The comparison of the experimental and calculated infrared (IR), Raman, and nuclear magnetic resonance (NMR) spectra has indicated that the experimental spectra are formed from the superposition of the spectra of two lowest energy conformers of the compound. So, it was concluded that the compound simultaneously exists in two optimized conformers in the ground state. Also the natural bond orbital (NBO) analysis has supported the simultaneous exiting of two conformers in the ground state. The calculated optimized geometric parameters (bond lengths and bond angles) and vibrational frequencies for both the lowest energy conformers were seen to be in a well agreement with the corresponding experimental data.

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