Steven L. Richardson

Density-functional theory calculation of the intermolecular exchange interaction in the magnetic Mn 4 dimer

The dimeric form of the single-molecule magnet

Density functional-based prediction of the electronic, structural, and vibrational properties of the energetic molecule: octanitrocubane

[{\mathrm{Mn}}_{4}{\mathrm{O}}_{3}{\mathrm{Cl}}_{4}({\mathrm{O}}_{2}\mathrm{CEt}{)}_{3}(\mathrm{py}{)}_{3}{]}_{2}

IMPROVED AIRY FUNCTION FORMALISM FOR STUDY OF RESONANT TUNNELING IN MULTIBARRIER SEMICONDUCTOR HETEROSTRUCTURES

recently revealed interesting phenomena: no quantum tunneling at zero field and tunneling before magnetic-field reversal. This is attributed to substantial antiferromagnetic exchange interaction between different monomers. The intermolecular exchange interaction, electronic structure, and magnetic properties of this molecular magnet are calculated using density-functional theory within generalized-gradient approximation. Calculations are in good agreement with experiment.

DETERMINATION OF THE HEATS OF FORMATION OF CCCN AND HCCCN

Abstract We have performed density functional calculations on the recently discovered energetic molecule, octanitrocubane C 8 (NO 2 ) 8 . We predict a strongly exothermic dissociation energy and calculate the ionization potentials, electron affinities and vibrational spectra. We predict that the isolated molecule exhibits a symmetry which is higher than that found in the solid. The vibrational density of states shows strong Raman activity at low frequencies and strong IR intensities at high frequencies. We identify a low-energy anharmonic mode which is consistent with the experimentally assumed free torsional rotations of the NO 2 groups about their respective C–N axes.

Optical excitation energies, Stokes shift, and spin-splitting of C24H72Si14

We show that our exact one‐dimensional Airy function formalism for studying electron resonant tunneling in multibarrier semiconductor heterostructures is an improvement on a previous calculation of Brennan and Summers [J. Appl. Phys. 61, 614 (1987)]. We also clearly demonstrate that our method gives better agreement with the numerical approach of Vassell, Lee, and Lockwood [J. Appl. Phys. 54, 5206 (1983)] in calculating the transmission coefficient T(E) and current density J(E) for multibarrier semiconductor heterostructures.

Electronic structure and rebonding in the onionlike As@Ni 12 @As 20 cluster

The electronic structure, vibrational spectra, and thermodynamic stability of CCCN and HCCCN have been determined using ab initio molecular orbital theory. The heat of formation for HCCCN was determined using Gaussian‐2 theory (G2) and was found to be 91.5±2 kcal mol−1. There is good agreement between the G2 value and that determined using an isodesmic reaction (i.e., one in which both the number and types of bonds are conserved), which yields 90.7±2 kcal mol−1. The heat of formation for the CCCN radical is 178.2±2 kcal mol−1. These data are used to compute the bond dissociation energies in HCCCN, D0(C–C) and D0(C–H), which are important in assessing the chemistry in Titan’s atmosphere, as well as in other interstellar media.

Electronic charge densities at valence and conduction band edges of ZnSe and CdTe

As an initial step toward the synthesis and characterization of sila-diamondoids, such as sila-adamantane (Si(10)H(16),T(d)), the synthesis of a fourfold silylated sila-adamantane molecule (C(24)H(72)Si(14),T(d)) has been reported in literature [Fischer et al., Science 310, 825 (2005)]. We present the electronic structure, ionization energies, quasiparticle gap, and the excitation energies for the Si(14)(CH(3))(24) and the exact silicon analog of adamantane Si(10)H(16) obtained at the all-electron level using the delta-self-consistent-field and transitional state methods within two different density functional models: (i) Perdew-Burke-Ernzerhof generalized gradient approximation and (ii) fully analytic density functional (ADFT) implementation with atom dependent potential. The ADFT is designed so that molecules separate into atoms having exact atomic energies. The calculations within the two models agree well, to within 0.25 eV for optical excitations. The effect of structural relaxation in the presence of electron-hole-pair excitations is examined to obtain its contribution to the luminescence Stokes shift. The spin-influence on exciton energies is also determined. Our calculations indicate overall decrease in the absorption, emission, quasiparticle, and highest occupied molecular orbital-lowest unoccupied molecular orbital gaps, ionization energies, Stokes shift, and exciton binding energy when passivating hydrogens in the Si(10)H(16) are replaced with electron donating groups such as methyl (Me) and trimehylsilyl (-Si(Me)(3)).

Electronic structure, vibrational stability, and predicted infrared-Raman spectra of the As20, As@Ni12, and As@Ni12@As20 clusters

We present the ab initio study of the geometry, electronic structure, charged states, bonding, and vibrational modes of the recently synthesised fullerene-like As@Ni 1 2 @As 2 0 cluster which has icosahedral point symmetry[M. J. Moses, J. C. Fettinger, and B. W. Eichhorn, Science, 300, 778 (2003)]. We show that the molecule is vibrationally stable and will be electronically most stable in its - 3 oxidation state in the condensed phase and in -2 state in the gas phase. We examine the bonding in this unusually structured molecule from charge transfer between atoms, infrared and Raman spectra, and charge-density isosuriaces.

First-principles DFT study of the structural, electronic and vibrational properties of azidopentazole

Abstract The empirical pseudopotential method (EPM) is used to calculate electronic charge densities at selected k points of the valence and conduction band edges of two II–VI semiconductors: ZnSe and CdTe.

Can chlorine anion catalyze the reaction of HOCl with HCl

Recently an inorganic fullerine-like [As@Ni(12)@As(20)](3-) onion with near-perfect icosahedral symmetry in the crystalline phase was reported [M. J. Moses, J. C. Fettinger, and B. W. Eichhorn, Science 300, 778 (2003)]. This paper presents a detailed computational study in the framework of density functional theory on various aspects of this molecule. The electronic structure of the As@Ni(12)@As(20) is investigated in its neutral as well as -3 charged state together with its subunits As(20) and As@Ni(12) by the all electron linear combination of Gaussian-type orbitals method. The bonding is studied by examining the integrated charge within atomic sphere, the electron localization function, changes in the electron density distribution, and from vibrational modes. We find that strong covalent As-As bonds seen in isolated As(20) become weaker in the As@Ni(12)@As(20) and strong covalent As-Ni bonds are formed. The structural stability of all four clusters is examined by analyzing the energetics and by calculating the vibrational frequencies. Further, the infrared and Raman spectra is predicted for both the neutral and charged As@Ni(12)@As(20) clusters. Finally, the energy barrier for removal of a single arsenic atom is calculated for the neutral As@Ni(12)@As(20) cluster.