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Search Results: 1 - 10 of 12823 matches for " <i>Ab Initio</i> Calculation "
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Theoretical Calculation of the Low-Lying Electronic States of the Molecule PbO  [PDF]
Diana Kaeen, Mahmoud Korek, Saleh Nabhan Abdulal, Ramadan Awad
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.68121
Abstract: The potential energy curves of the lowest 20 electronic states in the representation 2s+1Λ(±) of the molecule PbO have been investigated via ab initio CASSCF and MRCI (single and double excitations with Davidson correction) calculations. The spectroscopic constants such as vibrational harmonic frequency ωe, the internuclear distance at equilibrium Re, the rotational constant Be, and the electronic transition energy Te with respect to the ground state have been calculated along with the permanent dipole moment for the different bound investigated electronic states. By using the canonical functions approach, the eigenvalues Ev, the rotational constant Bv and the abscissas of the turning points Rmin and Rmax have been calculated. The comparison of these values with those available in the literature shows a very good agreement.
Electronic and Optical Properties of Rare Earth Oxides: Ab Initio Calculation  [PDF]
Sezen Horoz, Sevket Simsek, Selami Palaz, Amirullah M. Mamedov
World Journal of Condensed Matter Physics (WJCMP) , 2015, DOI: 10.4236/wjcmp.2015.52011
Abstract: In this work, we have investigated the electronic and optical properties of the technologically important rare earth oxide compounds—X2O3 (X: Gd, Tb) using the density functional theory within the GGA. The band structure of X2O3 have been calculated along high symmetry directions in the first brillouin zone. The real and imaginary parts of dilectric functions and the other optical responses such as energy-loss function, the effective number of valence electrons and the effective optical dielectric constants of the rare earth sesquioxides (Gd2O3 and Tb2O3) were calculated.
Theoretical Study of the Triplet Electronic States of the BP Molecule  [PDF]
Mahdi Mansour, Nayla El-Kork, Mahmoud Korek
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.68119
Abstract: The Complete Active Space Self Consistent Field (CASSCF) with Multi Reference Configuration Interaction (single and double excitation with Davidson correction) MRCI + Q method has been used to investigate the potential energy curves of the 17 low-lying triplet electronic states of the molecule BP. The harmonic vibrational frequency ωe, the inter-nuclear distance at equilibrium Re, the rotational constant Be, the electronic energy with respect to the minimum ground state energy Te, and the permanent dipole moment have been also calculated. A literature review shows a strong correlation between our investigated data and those previously published either theoretically or experimentally. This work introduces, for the first time, a study of 14 new electronic states. Our spectroscopic data can be a conducive to further work on BP molecule in both experimental and theoretical research.
Electronic Structure of the Cesium Oxide Molecule CsO  [PDF]
Diana Kaeen, Mahmoud Korek, Saleh Nabhan Abdulal
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.613194
Abstract: Adiabatic potential energy curves of 12 doublet and quartet lowest spinless electronic states of the molecule CsO have been investigated via ab initio CASSCF and MRCI (doublet and quartet excitations with Davidson correction) calculations. The spectroscopic constants such as vibrational harmonic frequency ωe, the internuclear distance at equilibrium Re, the rotational constant Be, and the electronic transition energy Te of the ground and the excited electronic states have been calculated by fitting the energy values around the equilibrium position to a polynomial in terms of the internuclear distance. The comparison of these values to those available in the literature shows a good agreement.
Ab-Initio Calculations of 27 Electronic States of the BP+ Ion-Molecule  [PDF]
Mahdi Mansour, Nayla El-Kork, Mahmoud Korek
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.613180
Abstract: The theoretical investigation of the potential energy curves, in the representation 2s+1Λ(+/-), of the 27 low-lying Doublet and Quartet electronic states of the BP+ molecular ion has been performed with the methods in quantum chemistry, the Complete Active Space Self Consistent Field (CASSCF) and the Multireference Configuration Interaction (MRCI) calculations. The harmonic vibrational frequency ωe, the inter-nuclear distance at equilibrium Re, the rotational constant Be, the electronic energy with respect to the minimum ground state energy Te, and the permanent dipole moment have also been calculated. Twenty-three new electronic states have been investigated here for the first time. The comparison between the values of the present work and those available in the literature for several electronic states shows a good agreement. These investigated data can be a conducive to further work on BP+ molecular ion in both experimental and theoretical research.
Theoretical Calculation of the Low-Lying Electronic States of the Molecule ScSe  [PDF]
Rawad Halabi, Mahmoud Korek
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.615233
Abstract: Theoretical investigation of the lowest electronic states of ScSe molecule, in the representation 2s+1Λ(+/-), has been performed via CASSCF and MRCI + Q (single and double excitations with Davidson correction) calculations. The calculated potential energy curves (PECs), permanent dipole moment curves (PDMCs), and spectroscopic constants are reported for the 14 lowest electronic states. The comparison of the present results with the rare available theoretical data in literature shows an overall good agreement. To the best of our knowledge, 13 electronic states of the ScSe molecule are not yet investigated either experimentally or theoretically; they are investigated in the present work for the first time.
Ab Initio Calculation of the Electronic States of ScTe Molecule below 19,500 cm-1  [PDF]
Rawad Halabi, Mahmoud Korek
Journal of Modern Physics (JMP) , 2016, DOI: 10.4236/jmp.2016.71010
Abstract: The potential energy curves (PECs) of the16 lowest electronic states in the representation 2s+1Λ (+/-) of the molecule ScTe have been investigated via ab initio CASSCF and MRCI (single and double excitations with Davidson correction) calculations. The permanent dipole moment curves (PDMCs) and the spectroscopic constants such as vibrational harmonic frequency ωe, the internuclear distance at equilibrium Re, the rotational constant Be, and the electronic transition energy Te with respect to the ground state have been calculated for the different bound investigated electronic states. The comparison of the present results with the rare available theoretical data in literature shows an overall good agreement. To the best of our knowledge, 15 electronic states of the ScTe molecule are not yet investigated either experimentally or theoretically, they are investigated in the present work for the first time.
Theoretical Calculation of the Low-Lying Electronic States of the Molecule BaS  [PDF]
Sally Shawa, Mahmoud Korek, Ghassan Younes, Nayla El-Kork
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.65066
Abstract: Complete Active Space Self Consistent Field (CASSCF) with Multireference Configuration Interaction (MRCI) and Rayleigh-Schrodinger Perturbation Theory (RSPT2-RS2) methods have been used to investigate the potential energy curves for the 12 low-lying singlet and triplet electronic states in the representation 2s+1Λ(+/-) of the molecule BaS with Davidson corrections. The harmonic frequency we, the internuclear distance Re, the electronic energy with respect to the ground state Te, the rotational constants Be and the permanent dipole moment have been calculated for these electronic states. The eigenvalues Ev, the rotational constants Bv, the centrifugal distortion constant Dv and the abscissas of the turning points Rmin and Rmax have been investigated using the canonical functions approach. Nine new electronic states have been investigated here for the first time. The comparison between the values of the present work and those available in the literature for several electronic states shows a good agreement.
Electronic Structure and Spectroscopic Studies of the Molecule ScS  [PDF]
Rawad Halabi, Mahmoud Korek
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.65059
Abstract: Theoretical investigation of the lowest electronic states of ScS molecule, in the representation 2s+1Λ(+/-), has been performed via CASSCF and MRCI (single and double excitations without Davidson correction) calculations. The calculated potential energy curves (PECs), permanent dipole moment curves (PDMCs), and spectroscopic constants are reported for the 10 lowest electronic states. The eigenvalues Ev, the rotational constants Bv, and the centrifugal distortion constants Dv have been calculated for various vibrational levels. The comparison of the present results with the available experimental data in literature shows an overall good agreement. To the best of our knowledge, 6 electronic states of the ScS molecule, between 11600 cm-1 and 15000 cm-1 are not yet observed experimentally and are investigated in the present work for the first time.
Bonding Characteristics of TiC and TiN  [PDF]
Kuiying Chen, Sami Kamran
Modeling and Numerical Simulation of Material Science (MNSMS) , 2013, DOI: 10.4236/mnsms.2013.31002
Abstract:

Using ab initio density functional theory calculations, the electron localization function (ELF) of typical transition metal carbide TiC and nitride TiN were computed and analyzed to reveal their nature of the chemical bonds. The ELF approach was initially validated through typical examples of covalent-bonding Diamond (C) and ionic-bonding sodium chloride NaCl. Our results clearly demonstrate the dominantly ionic bonding characteristics of TiC and TiN. It is also suggested that the high mechanical hardness of TiC and TiN can be explained without evoking strong covalence.

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