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81.
Gaussian expansions of the SCF functions for the first row atoms, boron through fluorine, in ground and low-lying electronic states have been generated under a wide range of radial weighting conditions by a full least-squares procedure. Typical results are presented and the quality of the wavefunctions obtained are analyzed in terms of regional electron densities and a variety of expectation values including energies. A novel method for recursive evaluation of repeated integrals of the error function, F
l
(,), is adopted and analyzed. These integrals are central quantities in the least-squares procedure employed.
Research performed under the auspices of the U.S. Atomic Energy Commission.
Summer student program participant, 1971, from Swarthmore College, Swarthmore, Pa. 相似文献
Zusammenfassung Entwicklungen nach Gaußfunktionen für SCF-Funktionen von Elementen der ersten Reihe (Bor bis Fluor) wurden für den Grundzustand und niedrige angeregte Zustände einer Methode der kleinsten Quadrate berechnet, wobei eine Reihe von radialen Gewichtsfaktoren benutzt wurden. Einige typische Ergebnisse werden mitgeteilt und die Qualität der erhaltenen Wellenfunktion wird mit Hilfe von regionalen Elektronendichten und einer Reihe von Erwartungswerten sowie der Energie geprüft. Eine neue Methode für die rekursive Auswertung der mehrfachen Integrale der Fehlerfunktion F l (, ) wird angewendet und analysiert. Diese Integrale sind von zentraler Bedeutung in der benutzten Methode der kleinsten Quadrate.
Résumé Engendrement de représentations gaussiennes des fonctions SCF pour les atomes de la première ligne, du bore au fluor, dans les états électroniques fondamentaux et faiblement excités, avec un large éventail de conditions de pondération radiale obtenues par une procédure de moindres carrés. Des résultats typiques sont présentés et les qualités des fonctions d'onde obtenues sont analysées en fonction des densités électroniques par régions et de différentes valeurs moyennes dont les énergies. Adoption et analyse d'une nouvelle méthode pour l'évaluation récursive d'intégrales répétées de la fonction d'erreur F l (,). Ces intégrales sont des quantités centrales dans les procédures de moindres carrés utilisées.
Research performed under the auspices of the U.S. Atomic Energy Commission.
Summer student program participant, 1971, from Swarthmore College, Swarthmore, Pa. 相似文献
82.
The syntheses and structures of two new compounds are reported. The first compound, [Cr(CO)4]2[C4F2(PPh2)4], obtained from Cr(CO)4(PPh2H)2 and CF3CCF3 in the presence of one equivalent of BuLi has a structure with the ligand 1,2,3,4-tetrakis(diphenylphosphino)-1,4-difluorobutadiene chelating to two Cr(CO)4 groups via the 1,4 and 2,3 phosphine groups. A mechanism for the formation of this compound is suggested which involves sequential deprotonation of a phosphine, nucleophilic attack on the fluorocarbon, and fluoride ion elimination. The second compound, CrC36H28P2O7, arises from a similar base promoted reaction of Cr(CO)4-(PPhH2)2 and PhCCCOOEt. Here the expected initial product from cyclization of these reactants acts as a nucleophile to attack a second equivalent of the acetylene. The intermediate carbanion from this reaction can undergo a ring closure by displacement of OEt-, giving the observed product. 相似文献
83.
Matthew S. Johnson Keith T. Kuwata Chi-Kin Wong Mitchio Okumura 《Chemical physics letters》1996,260(5-6):551-557
The infrared spectrum of the ionic cluster I−(H2O) was recorded from 3170 to 3800 cm−1 by vibrational predissociation spectroscopy. A strong multiplet observed at 3415 cm−1 and a narrow band at 3710 cm−1 were assigned as a hydrogen-bonded OH stretch and free OH stretch respectively, indicating that H2O forms a single hydrogen bond with the iodide anion. Ab initio vibrational frequencies and intensities were computed at the second-order Møller-Plesset (MP2) level for the minimum energy configuration, a nearly linear hydrogen-bonded isomer, and for a low-lying saddlepoint, a symmetric C2v bridged isomer. The spectrum predicted for the hydrogen-bonded isomer agreed well with experiment. 相似文献
84.
Xiaoqin Liang Wenxu Zheng Ning-Bew Wong Yuanjie Shu Anmin Tian 《Journal of Molecular Structure》2005,732(1-3):127-137
The keto–enol tautomerism of cyameluric acid, both in gas phase and in water and methanol solution, has been studied at the B3LYP/6-31++g(d,P) level of theory in this paper. The harmonic frequencies of all the structures are calculated. The results show that the transition states of the tautomerism are 4-membered ring conformations in gas phase, whereas 6-membered ring conformations in solution. In the first proton transfer, activation energy ΔE# is 56.4 and 50.9 kJ/mol for water and methanol solution, respectively, which is much lower than that in gas phase (163.2 kJ/mol). Solvent molecules (water and methanol) produce an important catalytic effect in the tautomerism, especially for methanol-solvated system. NBO analysis shows that there is a strong interaction between cyameluric acid and solvent molecules in transition states. AIM charge analysis indicates that the keto–enol tautomerism shows a certain degree of proton transfer character. From the reaction enthalpy and reaction rate point of view, keto–enol tautomerism in water-solvated and methanol-solvated system is easier than that in gas phase. The keto–enol tautomerisms are endothermic both in gas phase and in solution, so the enol forms are less stable than the keto ones. 相似文献
85.
This paper presents a mathematical model to describe a two-fluid electroosmotic pumping technique, in which an electrically non-conducting fluid is delivered by the interfacial viscous force of a conducting fluid; the latter is driven by electroosmosis. The electrical potential in the conducting fluid and the analytical solution of the steady two-fluid electroosmotic stratified flow in a rectangular microchannel was presented by assuming a planar interface between the two immiscible fluids. The effects of viscosity ratio, hold-up, concentration, and interfacial zeta potential are analyzed to show the potential feasibility of this technique. 相似文献
86.
Gies P Roy C McLennan A Pailthorpe M Hilfiker R Osterwalder U Monard B Moseley H Sliney D Wengraitis S Wong J Human S Bilimis Z Holmes G 《Photochemistry and photobiology》2003,77(1):58-67
In recent years the need to standardize measurement protocols for quantifying the degree of ultraviolet radiation (UVR) protection provided by clothing has led to the introduction of a number of standards around the world. To date, these standards have specified spectral measurements of UVR transmission by clothing and fabrics. Development of a standard test method has become an important part of the testing process, and this article presents results from an intercomparison involving 10 independent testing laboratories and 11 different UVR transmission measurement instruments. In addition to comparing the measured ultraviolet protection factors (UPF), this intercomparison also incorporates detailed scan results from all 10 laboratories and highlights differences in performance of the various instruments in different wavelength regions. Careful examination of these differences can indicate where changes to the systems could be made to allow improvements both in equipment performance and in agreement of the final results. The variability in the measurements of UPF in this study suggest that the protection categories in standards may need to be broadened. 相似文献
87.
A trinuclear heterobimetallic Ru(II)/Pt(II) complex, cis-{Ru(phen)2[CN-Pt(DMSO)Cl2]2} (phen = 1,10-phenanthroline), is able to function as a "switch-on" luminescent chemodosimeter for sulfhydryl-containing amino acids and peptides via specific binding of the amino acids/peptides with the Pt(II) centers and the subsequent cleavage of the Ru(II)-Pt(II) cyano-bridge. 相似文献
88.
89.
Wing Hung Wong 《Numerische Mathematik》1984,43(1):141-152
Summary The variational formulation of multivariate spline functions is generalized to include cases where the function has to satisfy inequality constraints such as positivity and convexity. Condition for existence and uniqueness of a solution is given. Approximation to the solution can be obtained by solving the variational problem in a finite dimensional subspace. Conditions for convergence and error estimates of the approximations are presented, both for interpolation problems and smoothing problems. The general theory is illustrated by specific examples including the volume-matching problem and the one-sided thin plate spline.This research is partially supported by the U.S. Army Contract No. DAAG 29-77-G-0207, and by NSF Grant No. MCS-8101836Part of this paper is based on Chapters 2 and 3 of the author's Ph. D. thesis. The author would like to express his sincere thanks to Professor Grance Wahba and to two referees for many helpful comments 相似文献
90.
H.C. Clark S.S. McBride N.C. Payne C.S. Wong 《Journal of organometallic chemistry》1979,178(2):393-408
The reaction of [Pt((F3C)CCH(CF3))(P(C2H5)3)2CH3OH]PF6 with allene in methanol affords a novel metallocyclic ethereal complex [CH3)(P(C2H5)3)2]PF6, which has been characterized by 1H, 2H, 19F and 31P NMR spectroscopy. Its structure has also been determined by a single crystal X-ray analysis. The crystal are monoclinic, space group P21/n, with cell dimensions a 20.012(5), b 17.222(5), c 8.902(3) Å and β 91.54(5)°. The structure was refined by full matrix least-squares methods on F, using 3097 unique observations collected by automated four circle diffractometer. Refinement converged at R 0.066. The Pt atom has a distorted square-planar coordination geometry, with cis P atoms, and PtP distances of 2.219(4) Å (trans to O) and 2.324(4) Å (trans to C). These results show the ethereal group is a weak ligand to platinum(II) but because of the chelating effect, its displacement by other ligands is thermodynamically not favorable. The mechanism of formation of the ethereal complex is also discussed. 相似文献