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Full-Text Articles in Physical Sciences and Mathematics
Theoretical Studies Of The Reactions Xhn → Xhn-1- + H+ And Xhn-1- + Sih4 → [Sih4xhn-1]-, Mark S. Gordon, Larry P. Davis, Larry W. Burggraf, Robert Damrauer
Theoretical Studies Of The Reactions Xhn → Xhn-1- + H+ And Xhn-1- + Sih4 → [Sih4xhn-1]-, Mark S. Gordon, Larry P. Davis, Larry W. Burggraf, Robert Damrauer
Mark S. Gordon
Ab initio and MNDO calculations have been carried out to evaluate the gas-phase acidities of closed-shell XHn compounds (X= C, N, 0, F, Si, P, S, Cl) and the affinities of silane for the XHn_1- anions. Fourth-order perturbation theory with extended basis sets reproduces the experimental gas-phase acidities to within 2 kcaljmol. Stable pentacoordinated silicon anions are found for X = H, C, N, 0, and F. In contrast, only marginally stable charge-dipole complexes are found for X = Si, S, and Cl.
Scaling All Correlation Energy In Perturbation Theory Calculations Of Bond Energies And Barrier Heights, Mark S. Gordon, Donald G. Truhlar
Scaling All Correlation Energy In Perturbation Theory Calculations Of Bond Energies And Barrier Heights, Mark S. Gordon, Donald G. Truhlar
Mark S. Gordon
We present and test a new method for scaling all correlation energy as estimated by M0ller-Plesset many-body perturbation theory with popular basis sets. Scale factors that may be useful for future applications are estimated from known bond dissociation energies. We also use scale factors to estimate the barrier heights for two hydrogen-transfer reactions, CH3 + H2 = CH4 + H and OH + CH4 = H20 + CH3•
Potential Primary Pyrolysis Processes For Disilane, Mark S. Gordon, Thanh N. Truong, Elizabeth K. Bonderson
Potential Primary Pyrolysis Processes For Disilane, Mark S. Gordon, Thanh N. Truong, Elizabeth K. Bonderson
Mark S. Gordon
Four competing unimolecular decomposition pathways for disilane are considered with use of MP4 energies obtained with an extended basis set and geometries obtained at the MP2/6-31G** computational level. The 1,1- and 1,2-eliminations of H2 and the elimination of silylene to form silane all have similar endothermicities, but the very high activation energy for the I ,2-elimination eliminates this process as a significant contributor at low energies. If disilene is formed in the thermal decomposition of disilane, the more likely source is its higher energy isomer silylsilylene via a relatively low energy I ,2-hydrogen shift.
Thermal Decomposition Of Silane, Mark S. Gordon, David R. Gano, J. Stephen Binkley, Michael J. Frisch
Thermal Decomposition Of Silane, Mark S. Gordon, David R. Gano, J. Stephen Binkley, Michael J. Frisch
Mark S. Gordon
The essential features of the potential energy surface for the thermal decomposition of silane have been calculated with extended basis sets, augmented by correlation corrections. It is predicted that the transition state for the molecular elimination lies 56.9 kcaljmol above silane. For the reverse reaction, the transition state is less than 2 kcal/mol above the separated fragments, silylene and molecular hydrogen, but 4.8 kcal/mol above a long-range potential well. In the latter, the silylene-H2 separation is 1.78 A, and the bond in H2 has stretched by more than 0.05 A. This indicates a significant electronic interaction between the fragments even …
Theoretical Studies Of Reactions Of Silanimine (H2sinh) And Its Isomer Aminosilylene (Hsinh2), Thanh N. Truong, Mark S. Gordon
Theoretical Studies Of Reactions Of Silanimine (H2sinh) And Its Isomer Aminosilylene (Hsinh2), Thanh N. Truong, Mark S. Gordon
Mark S. Gordon
The structure and reactivity of unsaturated singlet silicon-nitrogen compounds is theoretically investigated. Ab initio calculations demonstrate that the planar silylene HSiNH2 is the global minimum on the SiNH3 surface, with the planar doubly bound species H2SiNH 18 kcaljmol higher in energy. The internal rotational barriers are computed to be 26.9 kcaljmol for HSiNH2 and 37.9 kcaljmol for H2SiNH. However, the barrier for the inversion of H2SiNH is only 5.6 kcaljmol, so that inversion is favored over rotation for this species. The isomerization connecting H2SiNH to HSiNH2 has a barrier of 60 kcaljmol. The transition-state structures, as well as the exothermicities …
Π-Bond Strengths In Hp=Ph, H2p=P, Hp=Nh, And Hn=Nh, Michael W. Schmidt, Mark S. Gordon
Π-Bond Strengths In Hp=Ph, H2p=P, Hp=Nh, And Hn=Nh, Michael W. Schmidt, Mark S. Gordon
Mark S. Gordon
The chemistry of the HP=PH 1r bond found in the recently isolated diphosphene compounds is considered in several ways. The P=P 1r-bond strength is found by computing the rotation barrier (36 kcalfmol) and is compared to that found for HN=NH (63.5 kcalfmol) and HP=NH (47 kcalfmol). The structure of the HPPH anion is presented. Various electronic states of the H2PP isomer are considered and compared to those of HPPH. Dipole moments and PP stretching frequencies are reported. The concerted hydrogenation of diphosphene is also examined.