The Experts below are selected from a list of 48 Experts worldwide ranked by ideXlab platform

Yoshihiro Osamura - One of the best experts on this subject based on the ideXlab platform.

  • Orbital Exponent optimization for molecular self consistent field wave functions including the polarization function
    Canadian Journal of Chemistry, 1992
    Co-Authors: Kenro Hashimoto, Yoshihiro Osamura
    Abstract:

    We have applied the analytical energy gradient method with respect to the Orbital Exponents for molecular self-consistent-field wave functions including the polarization functions. The gradients for Gaussian-type functions in Huzinaga–Dunning's double zeta basis set with and without polarization functions were compared for some hydrides of the first-row elements. The changes in the gradients caused by the polarization functions were observed. It was found that the polarization functions on hydrogen play a role in reducing the gradients produced in the absence of these functions. Although optimization of the Exponents gives results depending on the molecules, the total energies as well as the dipole moments are insensitive to the Exponent values. We could confirm that the Exponents for Gaussian functions in the standard double zeta plus polarization basis set work adequately by coupling with the variational parameters for the simple hydrides even if they have gradients in the molecules. Keywords: Orbital e...

  • Orbital Exponent optimization with the analytical gradient method for molecular self consistent field wave functions
    Journal of Chemical Physics, 1991
    Co-Authors: Kenro Hashimoto, Yoshihiro Osamura
    Abstract:

    We have applied the energy gradient technique to optimize the Orbital Exponents of primitive Gaussian‐type functions for some simple molecules including first‐row elements, starting from the Exponent values of the Huzinaga–Dunning basis functions. It is found that the change of the Exponents clearly shows the better description of chemical bonds compared to the atomic Exponents, while the energy gain due to the Exponent optimization is very small. We can, however, confirm that the values of the Orbital Exponents optimized in atoms give extremely good description of the molecular wave functions. The scaling factor for a hydrogen atom in a molecular environment and the effect of the polarization functions for a hydrogen atom are also discussed.

  • Orbital Exponent optimization with the analytical gradient method for molecular self‐consistent‐field wave functions
    Journal of Chemical Physics, 1991
    Co-Authors: Kenro Hashimoto, Yoshihiro Osamura
    Abstract:

    We have applied the energy gradient technique to optimize the Orbital Exponents of primitive Gaussian‐type functions for some simple molecules including first‐row elements, starting from the Exponent values of the Huzinaga–Dunning basis functions. It is found that the change of the Exponents clearly shows the better description of chemical bonds compared to the atomic Exponents, while the energy gain due to the Exponent optimization is very small. We can, however, confirm that the values of the Orbital Exponents optimized in atoms give extremely good description of the molecular wave functions. The scaling factor for a hydrogen atom in a molecular environment and the effect of the polarization functions for a hydrogen atom are also discussed.

Kenro Hashimoto - One of the best experts on this subject based on the ideXlab platform.

  • Orbital Exponent optimization for molecular self consistent field wave functions including the polarization function
    Canadian Journal of Chemistry, 1992
    Co-Authors: Kenro Hashimoto, Yoshihiro Osamura
    Abstract:

    We have applied the analytical energy gradient method with respect to the Orbital Exponents for molecular self-consistent-field wave functions including the polarization functions. The gradients for Gaussian-type functions in Huzinaga–Dunning's double zeta basis set with and without polarization functions were compared for some hydrides of the first-row elements. The changes in the gradients caused by the polarization functions were observed. It was found that the polarization functions on hydrogen play a role in reducing the gradients produced in the absence of these functions. Although optimization of the Exponents gives results depending on the molecules, the total energies as well as the dipole moments are insensitive to the Exponent values. We could confirm that the Exponents for Gaussian functions in the standard double zeta plus polarization basis set work adequately by coupling with the variational parameters for the simple hydrides even if they have gradients in the molecules. Keywords: Orbital e...

  • Orbital Exponent optimization with the analytical gradient method for molecular self consistent field wave functions
    Journal of Chemical Physics, 1991
    Co-Authors: Kenro Hashimoto, Yoshihiro Osamura
    Abstract:

    We have applied the energy gradient technique to optimize the Orbital Exponents of primitive Gaussian‐type functions for some simple molecules including first‐row elements, starting from the Exponent values of the Huzinaga–Dunning basis functions. It is found that the change of the Exponents clearly shows the better description of chemical bonds compared to the atomic Exponents, while the energy gain due to the Exponent optimization is very small. We can, however, confirm that the values of the Orbital Exponents optimized in atoms give extremely good description of the molecular wave functions. The scaling factor for a hydrogen atom in a molecular environment and the effect of the polarization functions for a hydrogen atom are also discussed.

  • Orbital Exponent optimization with the analytical gradient method for molecular self‐consistent‐field wave functions
    Journal of Chemical Physics, 1991
    Co-Authors: Kenro Hashimoto, Yoshihiro Osamura
    Abstract:

    We have applied the energy gradient technique to optimize the Orbital Exponents of primitive Gaussian‐type functions for some simple molecules including first‐row elements, starting from the Exponent values of the Huzinaga–Dunning basis functions. It is found that the change of the Exponents clearly shows the better description of chemical bonds compared to the atomic Exponents, while the energy gain due to the Exponent optimization is very small. We can, however, confirm that the values of the Orbital Exponents optimized in atoms give extremely good description of the molecular wave functions. The scaling factor for a hydrogen atom in a molecular environment and the effect of the polarization functions for a hydrogen atom are also discussed.

Khalil H. Al Bayati - One of the best experts on this subject based on the ideXlab platform.

Maysoon A. Mahmood - One of the best experts on this subject based on the ideXlab platform.

Nazmul Islam - One of the best experts on this subject based on the ideXlab platform.

  • A NEW FORMULA FOR THE EVALUATION OF THE IONIZATION ENERGY BASED ON THE Orbital ExponentS OF THE ATOMS OF 118 ELEMENTS OF THE PERIODIC TABLE
    Journal of Theoretical and Computational Chemistry, 2010
    Co-Authors: Nazmul Islam, Arindam Jana
    Abstract:

    We propose a simple approach for the calculation of the ionization potentials of atoms in terms of their Orbital Exponents. The prescription is simple and utilizes only the simple Bohr equation with some modifications. We have pointed out that the atomic first ionization energy not only depends on the principal quantum number (n) but also on the azimuthal quantum number (l) of the Orbital (n, l) on which the electron of interest is present. The formalism is tested through the calculation of the atomic ionization potentials of 118 elements of the periodic table. The Orbital Exponent values for 118 elements of the periodic table are computed following the suggestions of Reed. The calculated numerical results for a number of atoms are shown to agree quite well with their experimental counterparts. To perform the validity tests of the present scale of ionization potential, various physico-chemical properties of the atoms are also correlated on the basis of the computed ionization potential data. It is found that the stability of the half filled configuration depends on the Orbital (n, l) on which the electron is present. The expressed periodic behavior and correlation of the most important physico-chemical properties of elements suggest that the present method of evaluation of the ionization potential of the atoms is quite a successful venture.

  • The wave mechanical evaluation of the absolute radii of atoms
    Journal of Molecular Structure-theochem, 2008
    Co-Authors: Dulal C. Ghosh, Raka Biswas, Tanmoy Chakraborty, Nazmul Islam, Sandip K. Rajak
    Abstract:

    Abstract Relying upon Slater’s definition that the maximum of the radial density function of the Orbital of the valence shell might be considered as a measure of the theoretical atomic radius and using the radial part of the Slater’s one-electron function, the STO’s, the formula for calculation of theoretical radii is derived as R  =  n ∗ / ξ , where n ∗ is the effective principal quantum number and ξ is the Orbital Exponent. We have computed the radii of the atoms of 103 elements of periodic table in terms of Orbital Exponent ( ξ ) evaluated following the rules laid down by Slater. Two more sets of atomic radii are evaluated using the same formula but Orbital Exponents taken from the Hartree–Fock non-relativistic calculation and the set of the Orbital Exponents computed from the effective nuclear charge determined by Mande Deshmukh and Deshmukh invoking Dirac’s relativistic equation using X-ray spectroscopic data. In order to explore the efficacy of the semi-empirical wave mechanical method of evaluation of atomic radii, a comparative critical study of the relative sizes of atoms evaluated by quantum mechanical semi-empirical, non-empirical Hartree–Fock and relativistic quantum mechanical methods is presented. Analysis of the results reveals that the set of radii computed through semi-empirical wave mechanical method satisfies all the essential criteria of the sizes of the atoms those follow from periodic table. It is observed that (i) the d-block and f-block contractions are nicely reproduced, (ii) the physical behaviour of profiles of the atomic radii against the atomic number is perfectly in accordance with the periodic law, (iii) the relativistic effect is reasonably incorporated in the computed radii of lanthanides and post lanthanide elements, (iv) the peculiar physical and chemical properties of Hg and Au atoms are perfectly justified in terms of their evaluated sizes, and (v) when compared with the results of a more reliable relativistic quantum mechanical calculation, it seems that, in the lanthanide series, the relativistic effect scintillates better in the sizes of the present calculation.