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1.
2.
Helga Fetter Berta Gamboa de Buen Jesús García-Falset 《Journal of Mathematical Analysis and Applications》2003,285(2):444-455
We consider a family of spaces wider than r-UNC spaces and we give some fixed point results in the setting of these spaces. 相似文献
3.
After carrying out a systematic basis set convergence study, we evaluate several ground state potential energy surfaces of the Ar-N(2) van der Waals complex at the coupled cluster singles and doubles model including connected triples corrections. We use the aug-cc-pVXZ (X=5,Q,D) and the daug-cc-pVQZ basis sets augmented with a set of 3s3p2d1f1g (denoted 33211) and 3s3p2d2f1g (denoted 33221) midbond functions, respectively. aug-cc-pVTZ-33211 results were available in the literature. The aug-cc-pV5Z-33211 (daug-cc-pVQZ-33221) surface is characterized by a T-shaped minimum at R(e)=3.709 (3.701) A and of 99.01 (102.50) cm(-1), and a linear saddle point at 4.260 (4.257) A and D(e)=75.28 (79.73) cm(-1). These results are compared with the values provided by the semiempirical potentials available, and those of previous theoretical studies. The basis set convergence of the intermolecular potentials is also analyzed. From the potentials the rovibronic spectroscopic properties are determined. We study the basis set convergence of the rotational frequencies. The binding parameters that characterized the aug-cc-pVTZ-33211 surface are reasonable, but the surface is not good enough to evaluate the microwave spectra. The aug-cc-pVQZ-33211 basis set results considerably improve the triple zeta and are close to the aug-cc-pV5Z-33211. Considering the small differences between the quadruple and the quintuple zeta surfaces, the latter results can be expected to be close to convergence. At this level the differences with respect to the accurate experimental frequencies are in the order of 0.7%. In the case of the daug-cc-pVXZ-33211,33221 (X=5,Q,T,D) series, the convergence of the interaction energies with respect to basis set improvement is not so smooth. The errors in the frequencies obtained with the daug-cc-pVQZ-33221 basis set with respect to experiment are in the order of 0.4%. 相似文献
4.
(±)-cis-γ-Irone( 1 ), a main constitutent of natural iris oil, has been stereoselectively synthesized from methyl (2E)-3 -[(2,2,4-trimethyl-3-cyclohexen-1-yl)methoxy]-2-propenoate (3) (6 steps, overall yield 14%). The cis-configuration as the exocyclic position of the double bond of 1 were secured by the thermal ene reaction of the β-(alkenyloxy)acrylate 3 yielding the 3-oxabicyclo [3,3,1] nonane derivative 5 . 相似文献
5.
A molecular mechanics force field for studying some beta-lactams was developed from ab initio and experimental data. The optimized parameters allowed accurate calculation of the geometries of both the compounds on which the parametrization was based and others on which the validity of the predictions was checked. © 1994 by John Wiley & Sons, Inc. 相似文献
6.
Roland Boese Dieter Bläser Michael Nussbaumer Tadeusz Marek Krygowski 《Structural chemistry》1992,3(5):363-368
The crystal and molecular structure of nitrobenzene was determined at 103 K by X-ray diffraction, yieldingR=0.034 and a highly precise geometry of the molecule (esds of bond lengths 0.001 Å and bond angles 0.1°). The bond angles in the ring agree very well with additive scheme based on angular substituent parameters. X-X electron density maps support the view that the C-N bond does not exhibit-character, and, hence, the nitro group interacts with the ring mostly by inductive effects. 相似文献
7.
Ab initio ground state potential energy surfaces are obtained from interaction energies calculated with the coupled cluster singles and doubles model including connected triples corrections [CCSD(T)] and the aug-cc-pVXZ (X=5,Q,T,D) basis sets augmented with two different sets of midbond functions (denoted 33221 and 33211). The aug-cc-pV5Z-33221 surface is characterized by a T-shaped 49.5 cm(-1) minimum at Re=3.38 Angstroms and a linear saddle point at 3.95 Angstroms with De=36.6 cm(-1). These results agree well with the values provided by the accurate semiempirical potentials available. The rovibronic spectroscopic properties are determined and compared to the available experimental data and previous theoretical results. We study the basis set convergence of the intermolecular potentials and the rotational frequencies. The aug-cc-pVTZ basis sets provide reasonable binding parameters, but seem not to be converged enough for the evaluation of the microwave spectra. The aug-cc-pVQZ basis sets considerably improve the triple zeta results. The differences between the results obtained with the aug-cc-pVTZ-33221 basis set surface and those with the aug-cc-pVQZ-33221 are smaller than those of the corresponding bases with the set of 33211 midbond functions. The aug-cc-pVQZ surfaces are close to the aug-cc-pV5Z, that are expected to be close to convergence. With our best surfaces the errors in the frequencies with respect to the accurate experimental results go down to 0.6%. 相似文献
8.
Four new two-ligand complexes of copper(II) with 2,2′-bipyridine and one of three different α-hydroxycarboxylic acids (lactic, H2LACO; 2-methyllactic, H2MLACO; and mandelic, H2MANO) were prepared. Complexes 1–3 of general formula [Cu(HL)2(bipy)]·nH2O (HL=monodeprotonated acid), were characterized by elemental analysis, IR, electronic and EPR spectroscopy, magnetic measurements and thermogravimetric analysis. Complexes 1 (HL=HLACO, n=2), 2 (HL=HMLACO, n=1) and 3a (the result of attempted recrystallization of 3, of formula [Cu(HMANO)(bipy)2](HMANO)·H2MANO·CH3CN were studied by X-ray diffractometry. The copper atom is in an elongated, tetragonally distorted octahedral environment in 1 and 2 and in 3a has a coordination polyhedron intermediate between a square pyramid and a trigonal bipyramid, as evaluated in terms of the parameter τ. In 1 and 2 the α-hydroxycarboxylato ligand is bidentate and monoanionic but in 3a there are three forms: a monodentate monoanion, a monoanionic counterion, and a neutral molecule. 相似文献
9.
From an accurate ground state intermolecular potential energy surface we evaluate the rovibrational spectrum of the Ne-HCl van der Waals complex. The intermolecular potential is obtained by fitting a considerable number of interaction energies obtained at the coupled cluster singles and doubles including connected triple excitations level and with the augmented correlation consistent polarized valence quintuple zeta basis set extended with a set of 3s3p2d1f1g midbond functions. This basis set is selected after a systematic basis set study carried out at geometries close to those of the three main surface stationary points. The surface is characterized by two linear minima, i.e. Ne-ClH and Ne-HCl, with distances from the Ne atom to the HCl center of mass of 3.398 and 3.833 angstroms, respectively; and binding energies of -65.10 and -66.85 cm(-1), respectively. These results agree well with the experimental data available in contrast to previous theoretical results. The rovibrational spectra calculated for the different isotopic species are also compared to the experiments. 相似文献
10.
A molecular mechanics force field was developed for systems bearing the N? C? O unit on the basis of 6-31G* and 4-21G “ab initio” calculations with full optimization of the geometry and experimental heats of formation. The parameters used, which implicitly included the anomeric effect, provided good geometric and energetic results, both for the compounds on which the parametrization was based and for others on which the validity of the predictions was checked. 相似文献