scholarly journals QUANTUM CHEMICAL MODELING OF THE MECHANISM OF ACTION OF INHIBITORS OF CORROSION AND HYDROGEN ABSORPTION OF STEEL AT PRESENCE OF SRB (BASED ON 1,4-QUINONE DERIVATIVES)

2017 ◽  
Vol 17 (2) ◽  
pp. 184-189
Author(s):  
G.S. Beloglazov ◽  
S.A. Teryusheva ◽  
S.M. Beloglazov
Keyword(s):  
Mechanism Of Action ◽  
Quantum Chemical ◽  
Hydrogen Absorption ◽  
Basis Set ◽  
Chemical Characteristics ◽  
Chemical Modeling ◽  
Hartree Fock ◽  
Derivatives Of ◽  
Quantum Chemical Computations ◽  
Steel St3

The results of quantum chemical computations of isolated molecules(derivatives of 1,4-quinone) performed by using restricted Hartree-Fock (RHF)method with the aid of Gaussian94 software in 3-21G basis set, are reported.Correlation coefficients between quantum chemical characteristics (QCC) of themolecules of inhibitors of corrosion and hydrogen absorption of steel St3 andexperimentally measured efficiencies of such species as the inhibitors in SRBcontaining media, have been calculated.

Non-nuclear attractors on Si–Si bond in quantum-chemical modeling as basis set inadequacy

2003 ◽  
Vol 288 (2-3) ◽  
pp. 159-169 ◽  
Author(s):  
O.A Zhikol ◽  
A.F Oshkalo ◽  
O.V Shishkin ◽  
O.V Prezhdo
Keyword(s):  
Quantum Chemical ◽  
Basis Set ◽  
Quantum Chemical Modeling ◽  
Chemical Modeling

Quantum chemical computations on rotational isomers of hydrogen nitrite and nitritomethane

1982 ◽  
Vol 381 (1781) ◽  
pp. 443-455 ◽  
Keyword(s):  
Excited States ◽  
Quantum Chemical ◽  
Dipole Moments ◽  
Basis Set ◽  
Electronic Transitions ◽  
Rotational Isomers ◽  
Transition Structures ◽  
Quantum Chemical Computations ◽  
Split Valence ◽  
Good Agreement

Ab initio molecular-orbital computations with a split-valence 4-31G basis set have been carried out on syn- and antiperiplanar conformers of both HONO and H 3 CONO, and on the transition structures in the unimolecular isomerization process. Calculated values of geometric structural and rotational parameters, dipole moments, wavenumbers of vibrational transitions, energies of vertical electronic transitions to both neutral and ionized excited states, and thermodynamic properties are compared with experimental data; generally good agreement is found. No explanation of the anomalous stability of antiperiplanar HONO has been discovered.

A Study of Reactivity of Model Compounds of Lignin Biopolymer

2021 ◽  
Vol 316 ◽  
pp. 75-80
Author(s):  
Oleg Kh. Karimov ◽  
Galina Yu. Kolchina ◽  
Eldar M. Movsumzade
Keyword(s):  
Aromatic Ring ◽  
Quantum Chemical ◽  
Density Functional ◽  
Nucleophilic Attack ◽  
Hydroxyl Group ◽  
Model Compounds ◽  
Hartree Fock ◽  
Quantitative Characteristics ◽  
Derivatives Of ◽  
Hybrid Density Functional

In the framework of method of the B3LYP hybrid density functional and the restricted Hartree-Fock method, quantum-chemical calculations of model compounds of lignin, i.e. derivatives of p-hydroxycinnamic alcohol were carried out. The structures and reactivity of coumaric, coniferyl and synapol alcohols were studied. Quantitative characteristics of the reactivity of these acids are given. It is found that the electronic structure of lignin is determined primarily by the charge distribution in its structural phenylpropane unit. In the molecules of all model compounds of lignin, the center for nucleophilic attack is the carbon of aromatic ring (E-ring) with a hydroxyl group, and in the molecule of synapol alcohol, this center is also the carbon of the aromatic ring (E-ring) with a methoxy group. In all three compounds, a center with an increased electron density appears on the Сβ carbon atom.

Quantum chemical modeling of new derivatives of ( E,E )-azomethines: Synthesis, spectroscopic (FT-IR, UV/Vis, polarization) and thermophysical investigations

2017 ◽  
Vol 1137 ◽  
pp. 335-348 ◽  
Author(s):  
Siyamak Shahab ◽  
Masoome Sheikhi ◽  
Liudmila Filippovich ◽  
Dikusar Evgenij Anatol’evich ◽  
Hooriye Yahyaei
Keyword(s):  
Quantum Chemical ◽  
Quantum Chemical Modeling ◽  
Chemical Modeling ◽  
Ft Ir ◽  
Derivatives Of

scholarly journals Quantum chemical simulation of MoO3 dispergation on hydroxylated SiO2 surface

Surface ◽  
2021 ◽  
Vol 13(28) ◽  
pp. 75-83
Author(s):  
D. B. Nasiedkin ◽  
◽  
M. O. Nazarchuk ◽  
A. G. Grebenyuk ◽  
L. F. Sharanda ◽  
...  
Keyword(s):  
Temperature Interval ◽  
Quantum Chemical ◽  
Basis Set ◽  
Structural Fragment ◽  
Thermally Induced ◽  
Sio2 Surface ◽  
Silanol Groups ◽  
Hartree Fock ◽  
Lcao Approximation ◽  
Chemical Simulation

Метою даної роботи є оцінка енергетичної сприятливості утворення різних молібдатних груп (≡Si‑O‑)2Mo(=O)2 та =Si(‑O‑)2Mo(=O)2 під час термічно ініційованого диспергування MoO3 на гідроксильованій поверхні SiO2. Для цього було здійснено квантовохімічне моделювання реакції O12Si10(OH)16 + MoO3 = O12Si10(OH)14O2MoO2 + H2O в температурному інтервалі 300–1100 K із використанням обмеженого методу Хартрі-Фока (наближення ЛКАО) з валентним базисом SBKJC (Stevens-Basch-Krauss-Jasien-Cundari). Кластер O12Si10(OH)16, який являє собою структурний фрагмент кристала β‑кристобаліту, був використаний як модель високогідроксильованої поверхні кремнезему. Ми розглянули дві структури молібдатних груп (≡Si‑O‑)2Mo(=O)2, прикріплених до кремнеземного кластера O12Si10(OH)16 через силанольні групи. Молібдатні групи (Etot ‑584.60147 Hartree), прикріплені до кремнеземного кластера через віддалені силанольні групи, виявляються більш енергетично вигідними, ніж молібдатні групи (Etot ‑584.56565 Hartree), прикріплені до кремнеземного кластера через сусідні силанольні групи. Енергія молібдатних груп =Si(‑O‑)2Mo(=O)2 (Etot ‑584.48399 Hartree), прикріплених до кремнеземного кластера O12Si10(OH)16 через силандіольні групи, менш енергетично вигідні в порівнянні з подібними групами, прикріпленими через силанольні групи, через більше напруження кута між зв’язками. Знайдено, що реакція O12Si10(OH)16 + MoO3 = O12Si10(OH)14O2MoO2 + H2O в температурному інтервалі 300–1100 K, змодельована шляхом квантовохімічних розрахунків, свідчить, що процес диспергування MoO3 на гідроксильованій поверхні SiO2 є енергетично вигідним. Експ The aim of the present work is to evaluate the energetic favourability of the formation of different molybdate species (≡Si‑O‑)2Mo(=O)2 and =Si(‑O‑)2Mo(=O)2 during the thermally induced MoO3 dispergation on hydroxylated SiO2 surface. In order to do this a quantum chemical modelling of the reaction O12Si10(OH)16 + MoO3 = O12Si10(OH)14O2MoO2 + H2O within the temperature interval of 300–1100 K was undertaken using the Restricted Hartree-Fock method (the LCAO approximation) with the SBKJC (Stevens-Basch-Krauss-Jasien-Cundari) valence basis set. The cluster O12Si10(OH)16 which represents a structural fragment of a β‑cristobalite crystal was used in this work as a model of highly hydroxylated silica surface. We considered two structures of molybdate (≡Si‑O‑)2Mo(=O)2 species attached to O12Si10(OH)16 silica cluster via silanol groups. Molybdate species (Etot ‑584.60147 Hartree) attached to silica cluster via distant silanols appeared more energetically favourable than molybdate species (Etot ‑584.56565 Hartree) attached to silica cluster via nearby silanols. The energy of molybdate =Si(‑O‑)2Mo(=O)2 species (Etot ‑584.48399 Hartree) attached to O12Si10(OH)16 silica cluster via silanediol group is less favourable energetically in comparison with those attached via silanol groups because of higher bond angle straining. The reaction O12Si10(OH)16 + MoO3 = O12Si10(OH)14O2MoO2 + H2O in the temperature interval of 300–1100 K which simulates by quantum chemical calculations the dispergation of MoO3 on hydroxylated SiO2 surface was found to be energetically favourable. The experimentally optimised temperature of ca. 800 K required for dispergation of MoO3 on hydroxylated SiO2 surface is determined by MoO3 evaporation and transportation via the gas phase. ериментальна оптимальна температура (близько 800 K), потрібна для диспергування MoO3 на гідроксильованій поверхні SiO2, визначається випаровуванням та перенесенням MoO3 в газовій фазі.

scholarly journals THERMOCHEMICAL PARAMETERS OF SOME SMALL PURE AND DOPED SILICON CLUSTERS

2018 ◽  
Vol 55 (6A) ◽  
pp. 18
Author(s):  
Nguyen Minh Tam
Keyword(s):  
Quantum Chemical ◽  
Large Error ◽  
Basis Set ◽  
Coupled Cluster ◽  
Electron Affinities ◽  
Silicon Clusters ◽  
Coupled Cluster Theory ◽  
Doped Silicon ◽  
Thermochemical Parameters ◽  
Quantum Chemical Computations

Quantum chemical computations of thermochemical parameters of several series of small pure and doped silicon clusters are reviewed. We analyzed the performance of the coupled-cluster theory with energies extrapolated up to complet basis set, CCSD(T)/CBS and the composite G4 method in determining the total atomization energies (TAE), standard heats of formation (∆fH0), electron affinities (EA) and ionization energies (IE) and other thermochemical parameters with respect to available experimental data. The latter were determined with large error margins.

scholarly journals Quantum chemical modeling of orthophosphoric acid adsorption sites on hydrated anatase surface

Surface ◽  
2020 ◽  
Vol 12(27) ◽  
pp. 20-35
Author(s):  
О. V. Filonenko ◽  
◽  
E. M. Demianenko ◽  
V. V. Lobanov ◽  
◽  
...  
Keyword(s):  
Water Molecule ◽  
Quantum Chemical ◽  
Formation Energy ◽  
Orthophosphoric Acid ◽  
Basis Set ◽  
Quantum Chemical Modeling ◽  
Energy Effect ◽  
Chemical Modeling ◽  
Adsorption Sites ◽  
Thermodynamic Probability

Quantum chemical modeling of orthophosphoric acid adsorption sites on the hydrated surface of anatase was performed by the method of density functional theory (exchange-correlation functional PBE0, basis set 6-31 G(d,p)). The influence of the aqueous medium was taken into account within the framework of the continual solvent model. The work uses a cluster approach. The anatase surface is simulated by a neutral Ti(OH)4(H2O)2 cluster. The results of analysis of the geometry and energy characteristics of all the calculated complexes show that the highest interaction energy is inherent to the intermolecular complex of orthophosphoric acid and hydrated surface of anatase, where the oxygen atom of the phosphoryl group (О=Р≡) forms a hydrogen bond with a hydrogen atom of the coordinated water molecule of Ti(OH)4(H2O)2 cluster and two hydrogen atoms of the hydroxyl groups of the orthophosphoric acid molecule form two hydrogen bonds with two oxygen atoms of the titanol groups. The formation energy effect of this complex is -134.0 kJ/mol. The formation energy effect of the complex with separated charges by the proton transfer from the molecule H3PO4 to the Ti(OH)4(H2O)2 cluster with the formation of dihydrogen phosphate anion and the protonated form of the titanol group (º) is -131.1 kJ/mol, so indicating less thermodynamic probability of such intermolecular interaction. The smallest thermodynamic probability (-123.9 kJ/mol) of complexation between orthophosphoric acid and hydrated anatase surface where a water molecule moves from the coordination sphere of the titanium atom. The calculation results indicate a possible adsorption of the H3PO4 molecule in an aqueous solution on the hydrated anatase surface. Taking into account the effect of the solvent within the polarization continuum insignificantly changes the adsorption energy, which is -44.5 kJ/mol; for vacuum conditions this value is -49.0 kJ/mol.

Analytic derivative theory based on the Hellmann–Feynman theorem

1992 ◽  
Vol 70 (2) ◽  
pp. 434-442 ◽  
Author(s):  
K. Hirao
Keyword(s):  
Present Theory ◽  
Basis Functions ◽  
Force Constants ◽  
Basis Set ◽  
Energy Derivatives ◽  
First Order ◽  
Hartree Fock ◽  
Derivative Method ◽  
Derivatives Of ◽  
Feynman Theorem

General formulae for the second, third, and fourth derivatives of the energy with respect to the nuclear coordinates of a molecule are derived from the Hellmann–Feynman theorem. Hurley's condition is used to obtain approximations to the first-order wavefunction, from which the second, third, and fourth energies can be obtained, leading to quadratic, cubic, and quartic force constants. The procedure is equivalent to minimizing the derivative energy by perturbed variation techniques. The expressions for these higher energy derivatives are much simpler than those of the direct analytic derivative method. The electrostatic calculation involves only one-electron integrals. The coupled Hartree–Fock equations to obtain the wavefunction derivatives become much simpler. The present theory provides a great conceptual simplification. However, the theory is correct only if the basis set is complete or basis functions are independent of the perturbation. Keywords: analytic derivative theory, Hellmann–Feynman theorem, force constants, the curvature theorem.

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