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1

Thermodynamic Study: C-H Bond Activation of Methane with OsO⁺

100%

Aynali F., Altun Ciftcioglu G.

Acta Physica Polonica A

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2015

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vol. 128

|

issue 2B

B-167-B-169

EN

Catalysis plays a critical role in the accomplishment of industrially significant chemical transformations, by requiring less energy investment in underlying processes. Computational chemistry has had a pronounced impact on the understanding of the role of catalysts at the atomic and molecular level, contributing to design of more efficient catalysts. In this study, we compute thermochemical properties attending C-H bond activation of methane by OsO^+ and enabling subsequent dehydrogenation and dehydration reactions. It is found that the dehydrogenation channel is thermodynamically more favorable. This study should contribute to the understanding of C-H bond activation using homogeneous catalysis of partial oxidation of natural gas (methane) leading to formation of the easily transported liquid fuel methanol.

2

Theoretical Analysis of the Electronic Ground and Excited Franck-Condon State of 2-Alkylamino-(3, 5, or 6)-Methyl-4-Nitropyridine N-oxides

80%

Deperasińska I., Makarewicz A., Szemik-Hojniak A.

Acta Physica Polonica A

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2007

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vol. 112

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issue S

S-71-S-84

EN

We theoretically characterised properties of the electronic ground and excited Franck-Condon state of 2-alkylamino-(3, 5, or 6)-methyl-4- -nitropyridine N-oxides. The obtained results of time-dependent density functional theory calculations are consistent with the experimental absorption spectra. The nature of the lowest excited states of the considered N-oxides molecules is discussed. Two excited singlet states (in the midst of four lowest states) have the charge-transfer character. These states have different charge-transfer contribution of the two electron donor groups to the same electron acceptor. In consequence, different conditions for the promotion of intramolecular proton transfer in excited state are created in each case.

3

Density Functional Theory Studies on Ir Spectra of the Triphenylene Derivatives. A Scaled Quantum Mechanical Force Field Approach

80%

Merkel K., Kocot A., Wrzalik R., Orgasińska B.

Acta Physica Polonica A

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2000

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vol. 98

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issue 5

525-531

EN

Density functional theory, B3-LYP with the 6-31G^{*} basis set was applied to study the structures and vibrational infrared spectra of triphenylene and the hexasubstituted triphenylene derivatives. The calculated force fields were scaled using the scaled quantum mechanical force field method. The predicted vibrational frequencies were compared with the experimental IR spectra (500-4000cm^{-1}). The spectra were interpreted and vibrational assignments were reported. This study shows that the scaled density functional force field approach enables, through the transferability of scale factors, good interpretation of vibrational spectra of large molecules.

4

Structure of Free Radical inγ-Irradiated 21-Hydroxyprogesterone (Deoxycorticosterone) Single Crystals. ESR/ENDOR and DFT Studies

80%

Szyczewski A., Pietrzak J., Möbius K.

Acta Physica Polonica A

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2005

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vol. 108

|

issue 1

119-126

EN

Single crystals of 21-hydroxyprogesterone have been γ-irradiated at 295 K and studied using X-band ESR and ENDOR. The structure of the one type radical has been determined on the basis of an analysis of the angular variation of the spectra. This radical is formed by abstraction of the hydrogen atom from the C(6) carbon, while the unpaired electron is delocalised onto the system O(3), C(3), C(4), C(5), C(6). Hyperfine splitting constants and unpaired electron density distribution have been calculated for the proposed radical structure by using the Gaussian98 set of programs. The results are in very good agreement with the experimental data. The effect of the hydrogen bond and biological activity on the anisotropy of α-hyperfine splitting tensor have also been discussed.

5

Natural Bond Orbital (NBO) Population Analysis of 1-Azanapthalene-8-ol

80%

Gangadharan R., Sampath Krishnan S.

Acta Physica Polonica A

|

2014

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vol. 125

|

issue 1

18-22

EN

The molecular structure of 1-azanapthalene-8-ol was calculated by the B3LYP density functional model with 6-31G(d,p) basis set by Gaussian program. The results from natural bond orbital analysis have been analyzed in terms of the hybridization of atoms and the electronic structure of the title molecule. The stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital analysis. The electron density based local reactivity descriptors such as the Fukui functions were calculated. The dipole moment (μ) and polarizability (α), anisotropy polarizability (Δ α) and first order hyperpolarizability (β_{tot}) of the molecule have been reported.

6

First Order Hyperpolarizabilities, NPA and Fukui Functions of Cyclohexanone by Density Functional Theory Method

80%

Gangadharan R., Sampath Krishnan S.

Acta Physica Polonica A

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2015

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vol. 127

|

issue 3

748-752

EN

The molecular structure of cyclohexanone was calculated by the B3LYP density functional model with 6-311++G(d,p) basis set by Gaussian program. The results from natural bond orbital analysis have been analyzed in terms of the hybridization of atoms and the electronic structure of the title molecule. The formation of hydrogen bond was investigated using natural bond orbital calculation. The electron density based local reactivity descriptors such as Fukui functions were calculated. The dipole moment (μ) and polarizability (α), anisotropy polarizability (Δα) and first order hyperpolarizability (β_{tot}) of the molecule have been reported. Thermodynamic properties of the title compound were calculated at different temperatures.

7

Proton Transfer in Strong Hydrogen Bonds Revealed by Infrared Spectra - Correlations between Structure and Spectra for the BrH : NH_3 Complex

70%

Szczepaniak K., Person W.

Acta Physica Polonica A

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2007

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vol. 112

|

issue S

S-19-S-38

EN

Our scope is to achieve an understanding of the relation between the infrared spectrum and structure of a strong hydrogen-bonded complex, BrH : NH$_3$, and how and why this relationship is affected by the environment surrounding the complex. A series of DFT/B3LYP/6-31G(d,p) calculations was carried out for this system to obtain its structure and spectrum in different dielectric fields characterized by their relative permittivities. Changes in structure and spectrum (both frequencies and intensities) as the relative permittivity changes are explored. Calculations of spectra are made first under the harmonic approximation. In the next step the effect of anharmonicity was estimated for several different dielectric fields. The calculated anharmonic spectrum (for ε_r = 1.6) is compared with the experimentally observed infrared spectrum of the complex isolated in an Ar matrix at 10 K, obtained in our laboratory. The calculated frequencies and relative intensities for all normal modes agree with the corresponding experimental data surprisingly well. The potential usefulness of structure-spectra correlations is explored.

8

Influence of Local Environment on the Electronic Structure and Magnetic Properties of Ni_{1-x}Cu_{x}MnSb Alloys

61%

Jezierski A., Szytuła A.

Acta Physica Polonica A

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2000

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vol. 97

|

issue 3

607-610

EN

The magnetic ordering in Ni_{1-x}Cu_{x}MnSb alloys changes from ferromagnetic (x=0) to antiferromagnetic (x=1). The X-ray and neutron diffraction showed that the systems crystallise in C1_{b} type structure. We present an influence of the local chemical ordering on the electronic and magnetic properties of Ni_{1-x}Cu_{x}MnSb alloys. The band structure and the magnetic moments were calculated by the spin-polarised linear muffin-tin orbital in the atomic sphere approximation method for the experimental values of the lattice parameters. The magnetic moment of Mn increases from 3.8 μ_{B} for x=0 to 4.18 μ_{B} for x=1.

9

Towards relativistic ECP / DFT description of chemical bonding in E112 compounds: spin-orbit and correlation effects in E112X versus HgX (X=H, Au)

51%

Zaitsevskii A., Rykova E., Mosyagin N., Titov A.

Open Physics

|

2006

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vol. 4

|

issue 4

448-460

EN

The relativistic effective core potential (RECP) approach combined with the spin-orbit DFT electron correlation treatment was applied to the study of the bonding of eka-mercury (E112) and mercury with hydrogen and gold atoms. Highly accurate small-core shape-consistent RECPs derived from Hartree-Fock-Dirac-Breit atomic calculations with Fermi nuclear model were employed. The accuracy of the DFT correlation treatment was checked by comparing the results in the scalar-relativistic (spin-orbit-free) limit with those of high level scalar-relativistic correlation calculations within the same RECP model. E112H was predicted to be slightly more stable than its lighter homologue (HgH). The E112-Au bond energy is expected to be ca. 25–30 % weaker than that of Hg-Au. The role of correlations and magnetic (spin-dependent) interactions in E112-X and Hg-X (X=H, Au) bonding is discussed. The present computational procedure can be readily applied to much larger systems and seems to be a promising tool for simulating E112 adsorption on metal surfaces.

Refine search results

Thermodynamic Study: C-H Bond Activation of Methane with OsO⁺

Theoretical Analysis of the Electronic Ground and Excited Franck-Condon State of 2-Alkylamino-(3, 5, or 6)-Methyl-4-Nitropyridine N-oxides

Density Functional Theory Studies on Ir Spectra of the Triphenylene Derivatives. A Scaled Quantum Mechanical Force Field Approach

Structure of Free Radical inγ-Irradiated 21-Hydroxyprogesterone (Deoxycorticosterone) Single Crystals. ESR/ENDOR and DFT Studies

Natural Bond Orbital (NBO) Population Analysis of 1-Azanapthalene-8-ol

First Order Hyperpolarizabilities, NPA and Fukui Functions of Cyclohexanone by Density Functional Theory Method

Proton Transfer in Strong Hydrogen Bonds Revealed by Infrared Spectra - Correlations between Structure and Spectra for the BrH : NH_3 Complex

Influence of Local Environment on the Electronic Structure and Magnetic Properties of Ni_{1-x}Cu_{x}MnSb Alloys

Towards relativistic ECP / DFT description of chemical bonding in E112 compounds: spin-orbit and correlation effects in E112X versus HgX (X=H, Au)