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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 …
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.
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.