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Jane S. Murray Richard Gilardi M. Edward Grice Pat Lane Peter Politzer 《Structural chemistry》1996,7(4):273-280
Tri-s-triazine and two ditetrazolodiazines are known to have unusually high crystal densities (for unsubstituted C, N, H compounds). We have used a nonlocal density functional procedure to compute the geometries and energies of these and three related molecules, and then calculated the ab initio SCF electrostatic potentials on their molecular surfaces. We attribute the high densities to the relatively small molecular volumes and the strong intermolecular attractions arising from highly varying surface potentials. The energy differences of the two ditetrazoles and their diazide tautomers were computed, as well as for the dinitro derivative of one of the former. 相似文献
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The role of quantization of vibrational coordinates in the electron jump model of alkali atom, dimer plus halogen molecule collisions is examined. Despite the bound states of the molecule ions involved, a classical approximation may offer good approximation over a wide collision energy range for the energy distributions of the ions in a single electron jump. Some results are calculated for K + Br2 and K2 + Br2. The theory assumes that the electron jump probability is governed by the electronic matrix element H12 alone. Elementary arguments are offered to suggest that this may be a reasonable approximation. 相似文献
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Measurements of total cross sections Qi for chemi-ionization in scattering of a K2 dimer beam by a range of halogen containing molecules, at translational energies E ~ 7–11 kcal mol-1, are reported. Substantial cross sections, Qi ~ 2–10 Å2 are exhibited by the halogen molecules Br2, ICl, IBr, I2. Distinctly lower values Qi ~ 0·1–0.2 Å2 are exhibited by BrCN and the mercuric and stannic halides, HgX2, SnX4. The results show a close correlation with the chemi-ionization exoergicities, particularly for formation of a K+,X- ion pair. These chemi-ionization data and results from previous reactive scattering studies are compared, in order to estimate relative reaction yields for different reaction paths. The reaction dynamics for K2 with halogen molecules and cyanohalides are rationalized in terms of the electronic structure of the potential surface, where the orientation of the K2 dimer plays a crucial role. 相似文献
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Margaret L. Scheuermann David W. Boyce Kyle A. Grice Werner Kaminsky Stefan Stoll William B. Tolman Ole Swang Karen I. Goldberg 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(25):6610-6613
[Pd(P(Ar)(tBu)2)2] ( 1 , Ar=naphthyl) reacts with molecular oxygen to form PdII hydroxide dimers in which the naphthyl ring is cyclometalated and one equivalent of phosphine per palladium atom is released. This reaction involves the cleavage of both C H and O O bonds, two transformations central to catalytic aerobic oxidizations of hydrocarbons. Observations at low temperature suggest the initial formation of a superoxo complex, which then generates a peroxo complex prior to the C H activation step. A transition state for energetically viable C H activation across a Pd peroxo bond was located computationally. 相似文献
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Politzer Peter Lane Pat Sjoberg Per Grice M. Edward Shechter Harold 《Structural chemistry》1995,6(4-5):217-223
Twelve molecules containing only C, N, O, and F, which are of interest in the context of energetic materials, were found to have true local energy minima at the HF/6-31G* computational level. Both HF/6-31G* and MP2/6-31G* geometries are presented. A density functional procedure was used to find gas phase heats of formation. These are strongly positive for most of the molecules. The nitroso group significantly increases H
o
f.25C
compared to the nitro analogue. 相似文献
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We report complete measurement of the spectral properties of photon pairs generated via spontaneous parametric downconversion. The measurements, which include not only single-photon spectra but also two-photon joint spectra, were performed for both cw and ultrafast-pumping configurations. In agreement with theoretical predictions, the spectra for the ultrafast-pumped case reveal asymmetries that are not present with cw pumping. 相似文献
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Jane S. Murray M. Edward Grice Peter Politzer James R. Rabinowitz 《Journal of computational chemistry》1990,11(1):112-120
The electrostatic potential V( r ) that the nuclei and electrons of a molecule create in the surrounding space is well established as a guide in the study of molecular reactivity, and particularly, of biological recognition processes. Its rigorous computation is, however, very demanding of computer time for large molecules, such as those of interest in recognition interactions. We have accordingly investigated the use of an approximate finite multicenter multipole expansion technique to determine its applicability for producing reliable electrostatic potentials of dibenzo-p-dioxins and related molecules, with significantly reduced amounts of computer time, at distances of interest in recognition studies. A comparative analysis of the potentials of three dibenzo-p-dioxins and a substituted naphthalene molecule computed using both the multipole expansion technique and Gaussian 82 at the STO-5G level has been carried out. Overall we find that regions of negative and positive V( r ) at 1.75 Å above the molecular plane are very well reproduced by the multipole expansion technique, with up to a 20-fold improvement in computer time. 相似文献
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Reactive scattering of O atoms with ICl molecules has been studied at an initial translational energy E = 40 kJ mol-1 using a supersonic beam of O atoms seeded in He and at E = 15 kJ mol-1 using O atoms seeded in Ne. Velocity distributions of OI product were measured by cross-correlation time-of-flight analysis. Full contour maps of the differential reaction cross-section have been obtained which show peaking almost equally in the forward and backward directions at both initial translational energies. The product translational energy distributions are consistent with a long-lived O-I-Cl collision complex dissociating via a loose transition state. The stability of the O-I-Cl complex is attributed to the low electronegativity of the central I atom compared with the peripheral atoms. This electronegativity ordering rule also determines the stability of the intermediates in the other reactions of oxygen atoms with halogen molecules. The mild peaking of the product angular distributions for O + ICl and IBr indicates that collision complexes have quite modest collision angular momenta L ~ 40 ? corresponding to impact parameters b ~ 1·4 Å and that the angular momentum of the OI molecule in the loose transition state may be approximately half the product orbital angular momentum. 相似文献