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Full-Text Articles in Physical Sciences and Mathematics
(On The) Observability Of Cubic (P8) Octaphosphorus, Michael W. Schmidt, Mark S. Gordon
(On The) Observability Of Cubic (P8) Octaphosphorus, Michael W. Schmidt, Mark S. Gordon
Mark S. Gordon
A recent MNDO calculation predicts that the hypothetical P8 is more stable than the observed gas-phase species P4. The ab initio calculations reported here predict just the opposite but do establish that P8 is more stable than another experimentally known form, P2. The relative enthalpies (kcaljmol) are found to be as follows: 4P2, 72.4; 2P 4, 0; P8, 30.4. A force field analysis proves P8 has a cubic structure. The bond length, vibrational frequencies, and photoelectron spectrum of P8 are predicted.
Studies Of Silicon-Phosphorus Bonding, Kenneth J. Dykema, Thanh N. Truong, Mark S. Gordon
Studies Of Silicon-Phosphorus Bonding, Kenneth J. Dykema, Thanh N. Truong, Mark S. Gordon
Mark S. Gordon
Ab initio calculations are presented for several species containing a silicon-phosphorus bond. The types of bonding studied include "normal" single, double, and triple bonds, as well as an ylide-like structure. The latter is found to be much less strongly bound than the carbon analogue, with a smaller stretching force constant than that in silylphosphine. The insertions of silylene into the phosphine bond and of phosphinosilylene into H2 are discussed, with the former being illustrated using localized molecular orbitals along the intrinsic reaction coordinate (IRC). Silylene to silene isomerizations in both the closed-shell singlet and the lowest triplet states of SiPH3 …
A Theoretical Study Of Fluorine Atom And Fluoride Ion Attack On Methane And Silane, Larry P. Davis, Larry W. Burggraf, Mark S. Gordon, Kim K. Baldridge
A Theoretical Study Of Fluorine Atom And Fluoride Ion Attack On Methane And Silane, Larry P. Davis, Larry W. Burggraf, Mark S. Gordon, Kim K. Baldridge
Mark S. Gordon
We have performed MNDO and ab initio calculations for reactions of fluorine atom attack on methane and silane and, in addition, fluoride ion attack on the same molecules in the case of MNDO. We modeled both substitution and abstraction reactions in each case. Results were compared with experimental data, where available. Comparisons show that MNDO usually does as well as the ab initio methods in reproducing experimental values for D.E's of these reactions, but MNDO predicts activation barriers too high in most cases. Nevertheless, MNDO does qualitatively agree with the ab initio result that, while carbon undergoes abstraction much more …
The Intrinsic Reaction Coordinate And The Rotational Barrier In Silaethylene, Michael W. Schmidt, Mark S. Gordon, Michel Dupuis
The Intrinsic Reaction Coordinate And The Rotational Barrier In Silaethylene, Michael W. Schmidt, Mark S. Gordon, Michel Dupuis
Mark S. Gordon
The intrinsic reaction coordinate (IRC) is a minimum-energy pathway connecting reactants to products via the transition state. An improved algorithm for the determination of an IRC is presented. The method is illustrated for the rotation of the silicon-carbon double bond in silaethylene. This IRC shows all coordinates vary smoothly during the rotation from the planar to twisted structures, except for a slight pyramidalization at carbon. The rotational barrier is found to be about 37 kcaljmol, in good agreement with experimental estimates.
Glass Formation And High Conductivity In The Ternary System Silver Iodide + Silver Arsenate (Ag3aso4) + Silver Metaphosphate (Agpo3): Host To Glassy .Alpha.-Silver Iodide?, Steve W. Martin, Alberto Schiraldi
Glass Formation And High Conductivity In The Ternary System Silver Iodide + Silver Arsenate (Ag3aso4) + Silver Metaphosphate (Agpo3): Host To Glassy .Alpha.-Silver Iodide?, Steve W. Martin, Alberto Schiraldi
Steve W. Martin
Wide regions of glass formation have been found in the ternary system xAgI + yAg,As04 + (1 - x - y)AgPO,. Glasses containing up to 75 mol 7% AgI can be formed in sections greater than 2 cm thick without signs of devitrification. Glass transition temperatures as high as 175 OC for glasses containing - 10 mol % AgI fall to -45 OC at the highest AgI content. An equivalent ratio of Ag1:N is defined and it is found that, for all glass-forming compositions, the electrical data as expressed in the Arrhenius form, u = A exp(-E,,/RT), log (./(a cm)-’), …
Electronic Structure Of The Phosphoryl And Thiophosphoryl Bonds, Michael W. Schmidt, Mark S. Gordon
Electronic Structure Of The Phosphoryl And Thiophosphoryl Bonds, Michael W. Schmidt, Mark S. Gordon
Mark S. Gordon
.The pho~phoryl bond is presented as a. resonan~e hybrid between singly and triply bound structures. The types of electromcally excited states and a number of their potential surfaces can be understood within the confines of a singly bound model: However, a detailed analysis of the electronic distribution within the ground state shows significant contribution from the tnpl~ bound structure. In fact, increasing the electronegativity of the ligands at phosphorus increases the contribution of t~e tnp~y bound structure, so that the. PO bond order approaches that of a double bond. The thiophosphoryl bond may be VIewed m much the same manner …
Molecular And Electronic Structures Of Metallaspiropentanes, Mark S. Gordon, Philip Boudjouk
Molecular And Electronic Structures Of Metallaspiropentanes, Mark S. Gordon, Philip Boudjouk
Mark S. Gordon
Recent efforts in this laboratory have concentrated on synthesizing metallaspiropentane compounds (I) with M = C, Si, Ge, Sn, Ni, and Zn. To date, the molecule with M = Si and R = methyl has been successfully prepared, 1 while attempts to synthesize the corresponding carbon compound have not reached fruition. This paper presents initial ab initio calculations on the species with M = C and Si and with R = H. Geometries for all species were calculated with the