... 90 (1979) 280. [7] G. Biaise and A. Nortier, Surface Sei. 90 (1979) 495. [8] JK Norskov and B... more ... 90 (1979) 280. [7] G. Biaise and A. Nortier, Surface Sei. 90 (1979) 495. [8] JK Norskov and BILundqvist, Phys. Rev. B19 (1979) 5661. [9] ML Yu, Phys. Rev. Letters 47 (1981) 1325. [10] RJ Colton, JE Campana, TM Barlak, JJ DeCorpo and JR Wyatt, Rev. Sei. Instr. ...
The different rates of self-consistent-field (SCF) convergence in the Hartree-Fock (HF) and X α m... more The different rates of self-consistent-field (SCF) convergence in the Hartree-Fock (HF) and X α methods are examined. The difference is due to the absence (HF) or presence (X α) of the self-Coulomb interaction of each orbital. As a result the occupied orbitals are stabilized (destabilized) in the HF (X α) method. A perturbative method is introduced which improves the rate of SCF convergence in X α at minimal increase in computational effort.
A variational method for fitting the Hartree-Fock exchange potential is investigated. The method ... more A variational method for fitting the Hartree-Fock exchange potential is investigated. The method has properties similar to an earlier method that successfully treats the direct part of the electron-electron Coulomb interaction in density-functional calculations. The present method is tested on atomic neon and should permit reliable linear combination of atomic orbital Hartree-Fock molecular calculations that grow in complexity only as the cube of the number of basis orbitals.
A Kinetic Monte Carlo (KMC) model is developed to simulate non-symmetrically the cathode side of ... more A Kinetic Monte Carlo (KMC) model is developed to simulate non-symmetrically the cathode side of a Yttria Stabilized Zirconia (YSZ) fuel cell, in order to translate experimental, and ultimately theoretical rates into an atomistic model of the cathode. The KMC model consists of a set of several electrochemical reaction rates, adopted from experiments and first-principles calculations. The KMC simulations are
Two possible joints between different types of carbon tubules are discussed. Both joints introduc... more Two possible joints between different types of carbon tubules are discussed. Both joints introduce a single pentagon-heptagon pair into the perfect hexagon bonding pattern of the two tubules. These two types of joints can be used to form composite tubules in which every carbon atom is threefold coordinated. The first type of joint removes or adds a single hexagon from the circumference of the tubule and the second joins specific ``crenelated'' and ``sawtooth'' tubules of significantly different radii at an angle of 30°.
In an attempt to perform thorough and accurate linear combination of atomic orbitals (LCAO) Xalph... more In an attempt to perform thorough and accurate linear combination of atomic orbitals (LCAO) Xalpha, calculations on C2 and Si2, the effects of basis set composition on the computed spectroscopic constants are investigated for the first time. The questions of how to tell if an adequate basis set has been found and what Xalpha state corresponds to the lowest state of 1Sigma+g symmetry which involves strong electron correlation effects are addressed. With the larger bases, general agreement with experiment and previous density functional calculations are obtained. Remarkable agreement with the configuration interaction (CI) calculations of Bruna et al. on Si2 is obtained if the fractional occupation number method of Slater et al. is used.
The method of Mintmire and Dunlap which variationally fits the Coulomb potential rather than the ... more The method of Mintmire and Dunlap which variationally fits the Coulomb potential rather than the charge density is extended to linear combination of Gaussian-type orbitals Xα calculations on molecules. This approach is more efficient than fitting the charge density since the same integrals are used to treat the Coulomb and exchange potentials. Furthermore, the required Fock matrix elements are simple overlap rather than Coulomb integrals. However, the method is somewhat less accurate than fitting the charge density in a test on H2.
Nonrelativistic and, where appropriate, scalar-relativistic linear combination of Gaussian-type o... more Nonrelativistic and, where appropriate, scalar-relativistic linear combination of Gaussian-type orbital (LCGTO) local density functional (LDF) calculations on Ti{C 28}, Ce{ 28}, Ti{C 28H 4}, Ce{C 28H 4}, the corresponding empty fullerene C 28, and the corresponding hydrogenated fullerene C 28H 4 are compared. The empty fullerene is tetravalent and strongly binds four hydrogen atoms on its exterior or a tetravalent atom inside. Combining a tetravalent endohedral atom with four exterior hydrogen atoms significantly weakens the two different sets of bounds and leads to an open-shell electronic structure.
... 90 (1979) 280. [7] G. Biaise and A. Nortier, Surface Sei. 90 (1979) 495. [8] JK Norskov and B... more ... 90 (1979) 280. [7] G. Biaise and A. Nortier, Surface Sei. 90 (1979) 495. [8] JK Norskov and BILundqvist, Phys. Rev. B19 (1979) 5661. [9] ML Yu, Phys. Rev. Letters 47 (1981) 1325. [10] RJ Colton, JE Campana, TM Barlak, JJ DeCorpo and JR Wyatt, Rev. Sei. Instr. ...
The different rates of self-consistent-field (SCF) convergence in the Hartree-Fock (HF) and X α m... more The different rates of self-consistent-field (SCF) convergence in the Hartree-Fock (HF) and X α methods are examined. The difference is due to the absence (HF) or presence (X α) of the self-Coulomb interaction of each orbital. As a result the occupied orbitals are stabilized (destabilized) in the HF (X α) method. A perturbative method is introduced which improves the rate of SCF convergence in X α at minimal increase in computational effort.
A variational method for fitting the Hartree-Fock exchange potential is investigated. The method ... more A variational method for fitting the Hartree-Fock exchange potential is investigated. The method has properties similar to an earlier method that successfully treats the direct part of the electron-electron Coulomb interaction in density-functional calculations. The present method is tested on atomic neon and should permit reliable linear combination of atomic orbital Hartree-Fock molecular calculations that grow in complexity only as the cube of the number of basis orbitals.
A Kinetic Monte Carlo (KMC) model is developed to simulate non-symmetrically the cathode side of ... more A Kinetic Monte Carlo (KMC) model is developed to simulate non-symmetrically the cathode side of a Yttria Stabilized Zirconia (YSZ) fuel cell, in order to translate experimental, and ultimately theoretical rates into an atomistic model of the cathode. The KMC model consists of a set of several electrochemical reaction rates, adopted from experiments and first-principles calculations. The KMC simulations are
Two possible joints between different types of carbon tubules are discussed. Both joints introduc... more Two possible joints between different types of carbon tubules are discussed. Both joints introduce a single pentagon-heptagon pair into the perfect hexagon bonding pattern of the two tubules. These two types of joints can be used to form composite tubules in which every carbon atom is threefold coordinated. The first type of joint removes or adds a single hexagon from the circumference of the tubule and the second joins specific ``crenelated'' and ``sawtooth'' tubules of significantly different radii at an angle of 30°.
In an attempt to perform thorough and accurate linear combination of atomic orbitals (LCAO) Xalph... more In an attempt to perform thorough and accurate linear combination of atomic orbitals (LCAO) Xalpha, calculations on C2 and Si2, the effects of basis set composition on the computed spectroscopic constants are investigated for the first time. The questions of how to tell if an adequate basis set has been found and what Xalpha state corresponds to the lowest state of 1Sigma+g symmetry which involves strong electron correlation effects are addressed. With the larger bases, general agreement with experiment and previous density functional calculations are obtained. Remarkable agreement with the configuration interaction (CI) calculations of Bruna et al. on Si2 is obtained if the fractional occupation number method of Slater et al. is used.
The method of Mintmire and Dunlap which variationally fits the Coulomb potential rather than the ... more The method of Mintmire and Dunlap which variationally fits the Coulomb potential rather than the charge density is extended to linear combination of Gaussian-type orbitals Xα calculations on molecules. This approach is more efficient than fitting the charge density since the same integrals are used to treat the Coulomb and exchange potentials. Furthermore, the required Fock matrix elements are simple overlap rather than Coulomb integrals. However, the method is somewhat less accurate than fitting the charge density in a test on H2.
Nonrelativistic and, where appropriate, scalar-relativistic linear combination of Gaussian-type o... more Nonrelativistic and, where appropriate, scalar-relativistic linear combination of Gaussian-type orbital (LCGTO) local density functional (LDF) calculations on Ti{C 28}, Ce{ 28}, Ti{C 28H 4}, Ce{C 28H 4}, the corresponding empty fullerene C 28, and the corresponding hydrogenated fullerene C 28H 4 are compared. The empty fullerene is tetravalent and strongly binds four hydrogen atoms on its exterior or a tetravalent atom inside. Combining a tetravalent endohedral atom with four exterior hydrogen atoms significantly weakens the two different sets of bounds and leads to an open-shell electronic structure.
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Papers by Brett Dunlap