Global geometry optimization of small silicon clusters at the level of density functional theory

1998 ◽  
Vol 99 (4) ◽  
pp. 241-247 ◽  
Author(s):  
Bernd Hartke
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Geometry Optimization ◽  
Silicon Clusters ◽  
Functional Theory ◽  
Global Geometry

scholarly journals CO oxidation catalysed by Pd-based bimetallic nanoalloys

2015 ◽  
Vol 17 (42) ◽  
pp. 28010-28021 ◽  
Author(s):  
Dennis Palagin ◽  
Jonathan P. K. Doye
Keyword(s):  
Density Functional Theory ◽  
Co Oxidation ◽  
Oxidation Reaction ◽  
Density Functional ◽  
Geometry Optimization ◽  
Energy Barriers ◽  
Functional Theory ◽  
Global Geometry ◽  
Co Oxidation Reaction

Density functional theory based global geometry optimization has been used to demonstrate the crucial influence of the geometry of the catalytic cluster on the energy barriers for the CO oxidation reaction over Pd-based bimetallic nanoalloys.

scholarly journals Computational Study of the Electron Spectra of Vapor-Phase Indole and Four Azaindoles

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 1947
Author(s):  
Delano P. Chong
Keyword(s):  
Density Functional Theory ◽  
Vapor Phase ◽  
Density Functional ◽  
Computational Study ◽  
Geometry Optimization ◽  
The Other ◽  
Functional Theory ◽  
Electron Spectra

After geometry optimization, the electron spectra of indole and four azaindoles are calculated by density functional theory. Available experimental photoemission and excitation data for indole and 7-azaindole are used to compare with the theoretical values. The results for the other azaindoles are presented as predictions to help the interpretation of experimental spectra when they become available.

Density functional theory investigation of the effect of axial coordination and annelation on the absorption spectroscopy of nickel(II) and vanadyl porphyrins relevant to bitumen and crude oils

2013 ◽  
Vol 91 (9) ◽  
pp. 872-878 ◽  
Author(s):  
Stanislav R. Stoyanov ◽  
Cindy-Xing Yin ◽  
Murray R. Gray ◽  
Jeffrey M. Stryker ◽  
Sergey Gusarov ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Polyaromatic Hydrocarbons ◽  
Geometry Optimization ◽  
Soret Band ◽  
Heavy Oils ◽  
Visible Absorption ◽  
Functional Theory ◽  
Axial Coordination ◽  
Td Dft

The vanadium and nickel components in heavy oils and bitumen are important impurities in catalytic processing and form aggregates with other asphaltene components. Metalloporphyrins are commonly analyzed using the characteristic Soret band in the UV–vis absorption spectrum. However, the Soret band of metalloporphyrins in petroleum is broadened and weaker than expected based on the concentration of Ni and V in heavy oils and the extinction coefficients of isolated porphyrins. We hypothesize that the low intensity and broadening of the Soret band could be due to axial coordination of the metal center or fusion (annelation) of aromatic rings on the porphyrin π-system. This hypothesis is examined using the density functional theory for geometry optimization and time-dependent density functional theory (TD-DFT) for calculation of excited states of nickel(II) and vanadyl porphyrins with axially coordinated ligands and annelated polyaromatic hydrocarbons. Predictions of the excited electronic states performed using the tandem of TD-DFT and conductor-like polarizable continuum model of solvation support this hypothesis and provide insight into the extent of Soret band broadening and intensity decrease due to coordination and annelation. These computational results, validated with respect to visible absorption spectra, are important for understanding asphaltene aggregation and spectroscopic characterization and suggest methods for removal of transition metals from heavy oil.

scholarly journals Влияние переходных металлов IIIВ-группы на формирование замкнутых германиевых кластеров: компьютерный эксперимент в рамках теории функционала плотности

2019 ◽  
Vol 21 (2) ◽  
pp. 182-190
Author(s):  
Nadezda A. Borshch ◽  
Sergey I. Kurganskii
Keyword(s):  
Density Functional Theory ◽  
Solid State ◽  
Electronic Properties ◽  
Magnetic Moment ◽  
Geometric Structure ◽  
Density Functional ◽  
Chem Phys ◽  
Silicon Clusters ◽  
Functional Theory ◽  
Doped Silicon

Представлены результаты моделирования пространственной структуры и электронных свойств кластеров MeGe16 - и MeGe20 - (Me = Sc, Y, Lu). Рассматривается возможность синтеза  пуллереноподобных кластеров и кластеров с другими типами замкнутых структур. Проведены сравнительные расчеты в рамках теории функционала плотности с использованием базиса SDD и трех различных потенциалов – B3LYP, B3PW91 и PBEPBE. Анализируется влияние выбора потенциала на результаты моделирования пространственной структуры кластеров и их электронного спектра. Оценка адекватности теоретических методов проводится путем сравнения рассчитанных электронных спектров с экспериментальными результатами по фотоэлектронной спектроскопии кластеров.     REFERENCES Kroto H. W., Heath J. R., O’Brien S. C., Curl R. F., Smalley R. E. C60: Buckminsterfullerene. Nature, 1985, v. 318, pp. 162-163. https://doi.org/10.1038/318162a0 Hiura H., Miyazaki, Kanayama T. Formation of Metal-Encapsulating Si Cage Clusters. Phys. Rev. Lett., 2001, v. 86, p. 1733. https://doi.org/10.1103/PhysRev-Lett.86.1733 Wang J., Han J. Geometries, stabilities, and electronic properties of different-sized ZrSin (n=1–16) clusters: A density-functional investigation. Chem. Phys., 2005, v. 123(6), pp. 064306–064321. https://doi.org/10.1063/1.1998887 Guo L.-J., Liu X., Zhao G.-F. Computational investigation of TiSin (n=2–15) clusters by the densityfunctional theory. Chem. Phys., 2007, v. 126(23), pp. 234704–234710.  https://doi.org/10.1063/1.2743412 Li J., Wang G., Yao C., Mu Y., Wan J., Han M. Structures and magnetic properties of SinMn (n=1–15) clusters. Chem. Phys., 2009, v. 130(16), pp. 164514–164522.  https://doi.org/10.1063/1.3123805 Borshch N. A., Berestnev K. S., Pereslavtseva N. S., Kurganskii S. I. Geometric structure and electron spectrum of YSi n− clusters (n = 6–17) Physics of the Solid State, 2014, v. 56(6), pp. 1276–1281. https://doi.org/10.1134/S1063783414060080 Borshch N., Kurganskii S. Geometric structure, electron-energy spectrum, and growth of anionic scandium-silicon clusters ScSin- (n = 6–20). Appl. Phys., 2014, v. 116(12), pp. 124302-1 – 124302-8. https://doi.org/10.1063/1.4896528 Borshch N. A., Pereslavtseva N. S., Kurganskii S. I. Spatial structure and electronic spectrum of TiSi n - Clusters (n = 6–18). Russian Journal of Physical Chemistry A, v. 88(10), pp. 1712–1718. https://doi.org/10.1134/S0036024414100070 Borshch N. A., Pereslavtseva N. S., Kurganskii S. I. Spatial and electronic structures of the germanium-tantalum clusters TaGe n − (n = 8–17). Physics of the Solid State, 2014, vol. 56(11), pp. 2336–2342. https://doi.org/10.1134/S1063783414110055 Huang X., Yang J. Probing structure, thermochemistry, electron affi nity, and magnetic moment of thulium-doped silicon clusters TmSi n (n = 3–10) and their anions with density functional theory. Mol. Model., 2018, v. 24(1), p. 29. https://doi.org/10.1007/s00894-017-3566-7 Zhang, Y., Yang, J., Cheng, L. J. Probing Structure, Thermochemistry, Electron Affi nity and Magnetic Moment of Erbium-Doped Silicon Clusters ErSin (n = 3–10) and Their Anions with Density Functional Theory. Sci., 2018, v. 29(2), pp. 301–311. https://doi.org/10.1007/s10876-018-1336-z Ye T., Luo C., Xu B., Zhang S., Song H., Li G. Probing the geometries and electronic properties of charged Zr2Si n q (n = 1–12, q = ±1) clusters. Chem., 2018, v. 29(1), pp. 139–146.  https://doi.org/10.1007/s11224-17-1011-2 Nguyen M.T., Tran Q. T., Tran V.T. A CASSCF/ CASPT2 investigation on electron detachments from ScSi n − (n = 4–6) clusters. Mol. Model., 2017, v. 23(10), p. 282. https://doi.org/10.1007/s00894-017-3461-2 Liu Y., Jucai Yang J., Cheng L. Structural Stability and Evolution of Scandium-Doped Silicon Clusters: Evolution of Linked to Encapsulated Structures and Its Infl uence on the Prediction of Electron Affi nities for ScSin (n = 4–16) Clusters. Chem., 2018, v. 57(20), pp 12934–12940. https://doi.org/10.1021/acs.inorgchem.8b02159

DENSITY FUNCTIONAL THEORY STUDY OF H2O ADSORPTION AND DISSOCIATION ON Al (111) SURFACE

2013 ◽  
Vol 12 (05) ◽  
pp. 1350035 ◽  
Author(s):  
LIXIA YANG ◽  
XIAOLI LEI ◽  
JUN FENG ◽  
YUXIN ZHANG ◽  
MINGXING LIU
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Catalytic Effect ◽  
Geometry Optimization ◽  
Vacancy Defect ◽  
Hydroxyl Group ◽  
Dissociation Pathway ◽  
Functional Theory ◽  
Lower Activation ◽  
Adsorption And Dissociation

Comparative study about the adsorption and dissociation behaviors of H2O molecule on clean and vacancy defective Al (111) surface was conducted by extensive density functional theory (DFT) calculations, the interaction mechanisms between H2O molecule and Al (111) surface were also figured out. Geometry optimization results indicated that H2O molecule was apt to be adsorbed at top site on these two kinds of surfaces, whereas, the adsorption configurations, the adsorption type and inclination of H2O molecule planes away from the normal were different. The calculated adsorption energies demonstrated that the adsorption of H2O molecule occurred more readily on vacancy defective Al (111) surface. The electron density distribution indicated that the vacancy defect enhanced the interactions between H2O molecule and surface Al atoms. Further analysis of the density of states (DOS) showed that the vacancy defect increased the number of bonding electrons between H2O molecule and surface Al atoms. The detailed exploration of dissociation pathways demonstrated that the dissociation of H2O molecule on these two kinds of surfaces was a two-step process: (1) H2O → H + OH , (2) OH → H + O . However, for each step the dissociation pathway variations on vacancy defective Al (111) surface were different with those on clean Al (111) surface. Compared with the first step, the dissociation of hydroxyl group into O atom and H atom was kinetically difficult. The calculated lower activation energy barriers on vacancy defective Al (111) surface showed that the vacancy defect had catalytic effect for the dissociation of H2O molecule to some extent, especially for the first step.

scholarly journals DNA-stabilized Ag–Au bimetallic clusters: the effects of alloying and embedding on optical properties

2016 ◽  
Vol 18 (32) ◽  
pp. 22311-22322 ◽  
Author(s):  
Dennis Palagin ◽  
Jonathan P. K. Doye
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Geometry Optimization ◽  
Structural Evolution ◽  
Density Functional Theory Calculations ◽  
Time Dependent ◽  
Bimetallic Clusters ◽  
Functional Theory ◽  
Global Geometry ◽  
Dependent Density

Global geometry optimization and time-dependent density functional theory calculations have been used to study the structural evolution and optical properties of AgnAun (n = 2–6) nanoalloys both as individual clusters and as clusters stabilized with the fragments of DNA of different size.

Density Functional Theory Studies of Electronic Structures and Hyperfine Interactions of Muonium in Imidazole

2015 ◽  
Vol 749 ◽  
pp. 134-138 ◽  
Author(s):  
Pek Lan Toh ◽  
Shukri Sulaiman ◽  
Mohamed Ismail Mohamed Ibrahim ◽  
Lee Sin Ang
Keyword(s):  
Density Functional Theory ◽  
Electronic Structures ◽  
Density Functional ◽  
Hyperfine Interactions ◽  
Geometry Optimization ◽  
Optimization Procedure ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Total Energies ◽  
Structure Calculations

We carried out ab initio electronic structure calculations in the frameworks of the Density Functional Theory (DFT) to study the electronic structures and hyperfine interaction of muonium (Mu) in imidazole (C3H4N2) and 1–methylimidazole (CH3C3H3N2). The local energy minima and hyperfine interactions of the Mu trapped at the three studies sites were determined by performing geometry optimization procedure. The results show the total energies for all three studied sites are close to one another. The Mu hyperfine interactions were also determined, with the corresponding values vary from 343.00 MHz to 471.28 MHz for the imidazole–Mu cluster, and from 380.21 MHz – 465.57 MHz to 475.93 MHz for the cluster of 1–methylimidazole–Mu, respectively.

scholarly journals Synthesis, Characterization, Catalytic Activity, and DFT Calculations of Zn(II) Hydrazone Complexes

Molecules ◽  
2020 ◽  
Vol 25 (18) ◽  
pp. 4043 ◽  
Author(s):  
Temiloluwa T. Adejumo ◽  
Nikolaos V. Tzouras ◽  
Leandros P. Zorba ◽  
Dušanka Radanović ◽  
Andrej Pevec ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Density Functional ◽  
Chemical Potential ◽  
Chemical Reactivity ◽  
Geometry Optimization ◽  
Coupling Reaction ◽  
Functional Theory ◽  
Reactivity Descriptors

Two new Zn(II) complexes with tridentate hydrazone-based ligands (condensation products of 2-acetylthiazole) were synthesized and characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy and single crystal X-ray diffraction methods. The complexes 1, 2 and recently synthesized [ZnL3(NCS)2] (L3 = (E)-N,N,N-trimethyl-2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethan-1-aminium) complex 3 were tested as potential catalysts for the ketone-amine-alkyne (KA2) coupling reaction. The gas-phase geometry optimization of newly synthesized and characterized Zn(II) complexes has been computed at the density functional theory (DFT)/B3LYP/6–31G level of theory, while the highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO and LUMO) energies were calculated within the time-dependent density functional theory (TD-DFT) at B3LYP/6-31G and B3LYP/6-311G(d,p) levels of theory. From the energies of frontier molecular orbitals (HOMO–LUMO), the reactivity descriptors, such as chemical potential (μ), hardness (η), softness (S), electronegativity (χ) and electrophilicity index (ω) have been calculated. The energetic behavior of the investigated compounds (1 and 2) has been examined in gas phase and solvent media using the polarizable continuum model. For comparison reasons, the same calculations have been performed for recently synthesized [ZnL3(NCS)2] complex 3. DFT results show that compound 1 has the smaller frontier orbital gap so, it is more polarizable and is associated with a higher chemical reactivity, low kinetic stability and is termed as soft molecule.

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