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Effects Of Surfaces On Dynamic Percolation, H. K. Janssen, B. Schaub, Beate Schmittmann
Effects Of Surfaces On Dynamic Percolation, H. K. Janssen, B. Schaub, Beate Schmittmann
Beate Schmittmann
The general epidemic process, which is a stochastic multiparticle process belonging to the universality class of dynamic percolation, is studied in a semi-infinite geometry. Critical exponents characterizing the fractal properties are calculated to O(ε) (ε=6-d, where d is the spatial dimension) with use of renormalization-group techniques.
Modified Broyden’S Method For Accelerating Convergence In Self-Consistent Calculations, Duane D. Johnson
Modified Broyden’S Method For Accelerating Convergence In Self-Consistent Calculations, Duane D. Johnson
Duane D. Johnson
A modification to Broyden’s method for obtaining stable and computationally efficient convergence in self-consistent calculations is developed and discussed. The method incorporates the advantages of two schemes proposed by Srivastava and by Vanderbilt and Louie without any increase in complexity. Its improvement over their methods is discussed. The present method is compared with two other widely used convergence methods, simple mixing and Anderson’s method, for the case of the disordered binary alloy Ni0.35Fe0.65 on the verge of a magnetic instability and is shown to be much improved in stability and rate of convergence.
Potential Energy Surfaces For The Reaction Si (Silicon) + H2o (Water), Shogo Sakai, Mark S. Gordon, Kenneth D. Jordan
Potential Energy Surfaces For The Reaction Si (Silicon) + H2o (Water), Shogo Sakai, Mark S. Gordon, Kenneth D. Jordan
Mark S. Gordon
The potential energy surfaces for the reactions of silicon atom (ID and 3P) with the water molecule were calculated by ab initio self-consistent field (SCF) methods. The transition states for the insertion of silicon atom into the D--H bond of water were also calculated by the multiconfigurational SCF method. It is found that the crossing point of the singlet and triplet surfaces along the insertion reaction paths is near the transition state for the triplet rearrangement from the Si:OH2 complex to HSiOH. The potential energy surfaces for the 1,2-hydrogen migration HSiOH- H2Si0 in the singlet and triplet states and the …
Relative Energies Of Silaethylene And Methylsilylene, Roger S. Grev, Gustavo E. Scuseria, Andrew C. Scheiner, Henry F. Schaefer Iii, Mark S. Gordon
Relative Energies Of Silaethylene And Methylsilylene, Roger S. Grev, Gustavo E. Scuseria, Andrew C. Scheiner, Henry F. Schaefer Iii, Mark S. Gordon
Mark S. Gordon
The energy difference between silaethylene (H2Si=CH2) and methylsilylene (SiHMe) has been determined with ab initio quantum chemical techniques. Large basis sets and a variety of methods for the inclusion of electron correlation effects have been employed. In direct contrast to the recent theoretical and experimental results of Shin, Irikura, Beauchamp, and Goddard, which suggested silaethylene was 10 kcaljmol more stable than methylsilylene, we find the energy difference to be nearer 4 kcal/mol.
Slip, Twinning, And Fracture At A Grain Boundary In The L12 Ordered Structure—Aς = 9 Tilt Boundary, Alexander H. King, M. H. Yoo
Slip, Twinning, And Fracture At A Grain Boundary In The L12 Ordered Structure—Aς = 9 Tilt Boundary, Alexander H. King, M. H. Yoo
Alexander H. King
The role of interaction between slip dislocations and a Σ = 9 tilt boundary in localized microplastic deformation, cleavage, or intergranular fracture in the Li2 ordered structure has been analyzed by using the anisotropic elasticity theory of dislocations and fracture. Screw superpartials cross slip easily at the boundary onto the (1$\overline 1$1) and the (001) planes at low and high temperatures, respectively. Transmission of primary slip dislocations onto the conjugate slip system occurs with a certain degree of difficulty, which is eased by localized disordering. When the transmission is impeded, cleavage fracture on the ($\overline 1$11) plane is predicted to …
Gas-Phase And Computational Studies Of Pentacoordinate Silicon, Robert Damrauer, Larry W. Burggraf, Larry P. Davis, Mark S. Gordon
Gas-Phase And Computational Studies Of Pentacoordinate Silicon, Robert Damrauer, Larry W. Burggraf, Larry P. Davis, Mark S. Gordon
Mark S. Gordon
We have demonstrated that a wide variety of pentacoordinate silicon anions (siliconates) should be stable and can be prepared by combining the predictive powers of MNDO and ab initio computational methods and the flowing afterglow (FA) experimental technique. MNDO has been used to compute the anion affinities of 91 siliconates; all but five of these are predicted to be stable with respect to the loss of an anion. Twenty-four siliconates, most of them previously unreported, have been prepared and studied in the FA. The MNDO predictions were, in general, consistent with the experimental results and with trends previously reported by …
Bulking Control With Ozonation In A Nutrient Removal Activated Sludge System, Johannes Van Leeuwen
Bulking Control With Ozonation In A Nutrient Removal Activated Sludge System, Johannes Van Leeuwen
Johannes van Leeuwen
The control of sludge bulking by ozonation was studied on four parallel pilot-scale (100 l/d) biological nutrient removal systems. Bulking was caused by filamentous organisms which typically occur in nutrient removal systems, i.e. Type 0092, Tpye 0041 and Microthrix parvicella. Continuous dosing of ozone, at 1; 2 and 4g O3/kg mixed liquor suspended solids (MLSS).d resulted in a diluted sludge volume index of about 50 ml/g less than the unozonated control. Ozonation was more effective in the sludge cycle than directly into the aeration basin. Nitrification-denitrification was not affected, not even at dosages of 30 g O3/kg MLSS.d. Biological phosphate …
Theoretical Studies Of Silabicyclobutanes And Silacyclobutenes, Cnsi4-Nh6 (N = 0-4), Jerry A. Boatz, Mark S. Gordon
Theoretical Studies Of Silabicyclobutanes And Silacyclobutenes, Cnsi4-Nh6 (N = 0-4), Jerry A. Boatz, Mark S. Gordon
Mark S. Gordon
The geometries of the silicon-substituted bicyclobutanes and cyclobutenes c.Si4-.H6 are predicted by using the 3-21G(d) basis set and SCF wave functions. Strain energies and heats of formation are predicted by using MP2/6-31G(d) energies in conjunction with the appropriate homodesmic reactions. Bent bond lengths are calculated by tracing the path of maximum electron density connecting two nuclei, with the 6-31 G(2d) basis set at the 3-21 G(d) structures.
Potentially Aromatic Metallocycles, Kim K. Baldridge, Mark S. Gordon
Potentially Aromatic Metallocycles, Kim K. Baldridge, Mark S. Gordon
Mark S. Gordon
Ab initio molecular orbital theory is used to characterize a series of metal-substituted benzene and cyclopentadiene structures, with the heteroatom taken from the block in the periodic table bounded by groups IV-VI and periods 2-5. Structures are predicted with the 3-21G* basis set and SCF wave functions. The calculated bond lengths and bond angles are in general within 0.04 A and 2°, respectively, of the available experimental values. As a measure of the de localization stabilization, !::.£and t::..H0 values for the appropriate bond separation and superhomodesmic reactions are calculated with 3-21 G* Hartree-Fock energies for these compounds and some smaller …
Theoretical Study Of The Decomposition Of Five-Coordinate Silicon Anions, Larry P. David, Larry W. Burggraf, Mark S. Gordon
Theoretical Study Of The Decomposition Of Five-Coordinate Silicon Anions, Larry P. David, Larry W. Burggraf, Mark S. Gordon
Mark S. Gordon
We have performed a theoretical study of the decomposition of the five-coordinate silicon anions (siliconates) H3(CH3)SiOH- and (CH3) 4SiOH-. These ions can be formed from hydroxide ion attack on methylsilane or tetramethylsilane, respectively. Both MNDO and ab initio calculations show that removal of methane from the five-coordinate structure is likely, via a transfer of the proton from the OH group to an adjacent methyl substituent. This process we term anionic dissociative proton transfer, because the transition state is one in which the methyl group being removed is almost completely dissociated to methide ion before the proton transfer takes place. This …
Algorithms And Accuracy Requirements For Computing Reaction Paths By The Method Of Steepest Descent, Bruce C. Garrett, Michael J. Redmon, Rozeanne Steckler, Donald G. Truhlar, Kim K. Baldridge, David Bartol, Michael W. Schmidt, Mark S. Gordon
Algorithms And Accuracy Requirements For Computing Reaction Paths By The Method Of Steepest Descent, Bruce C. Garrett, Michael J. Redmon, Rozeanne Steckler, Donald G. Truhlar, Kim K. Baldridge, David Bartol, Michael W. Schmidt, Mark S. Gordon
Mark S. Gordon
We present several algorithms for computing minimum energy reaction paths by the method of steepest descents of the potential energy and for interpolating reaction-path potentials. The algorithms are suited for use with global analytic potential surfaces or ab initio calculations of energies and gradients. The efficiencies of the various algorithms are demonstrated and compared by applications to several test cases.
Effects Of Chemical And Magnetic Disorder In Fe0.50mn0.50, Duane D. Johnson, F. J. Pinski, G. M. Stocks
Effects Of Chemical And Magnetic Disorder In Fe0.50mn0.50, Duane D. Johnson, F. J. Pinski, G. M. Stocks
Duane D. Johnson
We present the results of first‐principles calculations of the total energy and spin‐polarized electronic structure of disordered fcc Fe0.50Mn0.50. These self‐consistent calculations were performed using the Korringa–Kohn–Rostoker method and the coherent‐potential approximation (KKR‐CPA), using the local‐spin‐density approximation to treat exchange and correlation. We use a lattice constant of a=6.80 a.u.; information about stability can be inferred from calculated pressure and energy. The moments on the Fe and Mn sites are large but antiparallel to each other, resulting in a small net magnetization. A comparison of the electronic structure is made for fcc Fe, Mn, and FeMn in both the ferromagnetic …
Substituted Silabenzenes, Kim K. Baldridge, Mark S. Gordon
Substituted Silabenzenes, Kim K. Baldridge, Mark S. Gordon
Mark S. Gordon
Ab initio calculations have been carried out on a group of substituted monosilabenzenes. Twelve different substituents are considered (Cl, F, SH, OH, PH2, NH2, CH3, SiH3, N02, CN, OCH3, COOH), each placed in the four unique positions on the ring. The relative energies and stabilities, aromaticities (as measured by bond separation reactions), electron density distributions, and dipole moments of these compounds are considered and discussed with the aid of density difference plots.
Structure And Bonding In Cycloalkanes And Monosilacycloalkanes, Jerry A. Boatz, Mark S. Gordon, Richard L. Hilderbrandt
Structure And Bonding In Cycloalkanes And Monosilacycloalkanes, Jerry A. Boatz, Mark S. Gordon, Richard L. Hilderbrandt
Mark S. Gordon
The structural parameters and vibrational frequencies are predicted for the cycloalkanes C.H2• and silacycloalkanes SiC,_1H2n, n = 3-6, using the 3-21G* basis set and SCF wave functions. Bent bond lengths are predicted by tracing the paths of maximum electron density connecting atomic centers. Strain energies and heats of formation are predicted for these compounds and some smaller acyclic alkylsilanes by using MP2/6-31G(d) energies at the 3-21G* geometries and the appropriate homodesmic reactions.
Theoretical Study Of The Lowest Triplet Potential Energy Surface Of Silasilene, Shiro Koseki, Mark S. Gordon
Theoretical Study Of The Lowest Triplet Potential Energy Surface Of Silasilene, Shiro Koseki, Mark S. Gordon
Mark S. Gordon
Bent silasilene, SiSiH2 (C,, 3A"), which has been reported as a global minimum on the lowest triplet potential energy surface of Si2H2, is found to be higher in energy than planar silasilene (C2v, 3A2) by about 2 kcaljmol at the MP4SDTQ/6-31 ++G(d,p) level, suggesting that triplet silasilene (still the global minimum) must have a planar geometry. Trans-bent HSiSiH (C2h, 3Au) should be the most stable triplet disilyne, instead of the twisted structure reported earlier, while the cis-bent structure (C., 3 A") might be observable.
Theoretical Study Of The Hyperfine Fields Of Ni And Fe In Fcc Ni,Fe, Alloys, H. Ebert, H. Winter, B. L. Gyorffy, Duane D. Johnson, F. J. Pinski
Theoretical Study Of The Hyperfine Fields Of Ni And Fe In Fcc Ni,Fe, Alloys, H. Ebert, H. Winter, B. L. Gyorffy, Duane D. Johnson, F. J. Pinski
Duane D. Johnson
Using charge self-consistent cluster Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) band-structure calculations, the authors have studied the hyperfine fields on both Ni and Fe sites in the NixFe1-x alloys. To elucidate the influence of relativistic effects the hyperfine matrix elements have been calculated nonrelativistically as well as completely relativistically The dependence of the hyperfine fields on the environment of a given site has been studied by performing calculations for various atomic configurations around that site. The results of the work are compared with other theoretical data and with experiment.