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1.
Bernhard Metz Marcus Schweizer Hermann Stoll Michael Dolg Wenjian Liu 《Theoretical chemistry accounts》2000,104(1):22-28
A relativistic pseudopotential of the energy-consistent variety simulating the Tl21+ (1s– 4f) core has been generated by adjustment to multiconfiguration Dirac–Hartree–Fock data based on the Dirac–Coulomb–Breit Hamiltonian.
Valence ab initio calculations using this pseudopotential have been performed for atomic excitation energies and for spectroscopic
constants of the X0+ and A0+ states of TlX (X = F, Cl, Br, I). Comparison is made to experiment and to four-component density functional results.
Received: 22 June 1999 / Accepted: 5 August 1999 / Published online: 15 December 1999 相似文献
2.
A series of correlation-consistent basis sets are developed for Fe. Our best computed 5F–5D separation in the Fe atom is in excellent agreement with experiment. Our best estimate for the FeCO D
0 value is in good agreement with experiment. The 5Σ−–3Σ− separation in FeCO has an error of 3.6 kcal/mol; while the origin of this error is not clear, it is probably not due to the
basis set.
Received: 5 March 2001 / Accepted: 2 May 2001 / Published online: 9 August 2001 相似文献
3.
The MP2 and CCSD(T) basis set limit binding energies of various hydrogen-bonded clusters were estimated via basis set extrapolation
employing the correlation consistent aug-cc-pVDZ and modified aug-cc-pVDZ set containing extra polarization functions from
cc-pVTZ set. By adopting the optimal interval for the difference between the cardinal numbers (X) corresponding to two basis sets in the X
−3 type extrapolation scheme the estimated binding energies for (H2O)n and (HF)n (n=3−5) are shown to be close to the reference basis set limit values within the error bounds in many cases, manifesting the
significance of these basis sets in studying the structures and binding of large hydrogen-bonded clusters. 相似文献
4.
5.
6.
Jan M. L. Martin 《Theoretical chemistry accounts》1997,97(1-4):227-231
The coupling between improvement of the basis set and the valence electron correlation method has been studied quantitatively
for the total atomization energies (TAEs) of a number of small molecules, using basis sets of up to [7s6p5d4f3g2h/5s4p3d2f1g] quality. Very significant coupling is found to exist. Using a scaled basis set extrapolation beyond [6s5p4d3f2g/ 4s3p2d1f] at the MP2 or CCSD level, mean absolute errors of 0.18 and 0.15 kcal/mol, respectively, can be obtained for the TAEs of
a number of small polyatomic molecules, compared to 0.12 kcal/mol using CCSD(T) throughout.
Received: 7 February 1997 / Accepted: 6 May 1997 相似文献
7.
Krzysztof Miecznikowski James A. Cox Adam Lewera Pawel J. Kulesza 《Journal of Solid State Electrochemistry》2000,4(4):199-204
We describe a sol-gel approach by which iron hexacyanoferrate is immobilized in silica in a manner suited to investigation
by electrochemistry in the absence of a contacting liquid phase. Such physicochemical parameters as concentration of redox
sites (C
o) and apparent (effective) diffusion coefficient (D
app) are estimated by performing cyclic voltammetric and potential step experiments in two time regimes, which are characterized
by linear and spherical diffusional patterns, respectively. Values of D
app and C
o thereby obtained are 2.0 × 10−6 cm2 s−1 and 1.4 × 10−2 mol dm−3. The D
app value is larger than expected for a typical solid redox-conducting material. Analogous measurements done in iron(III) hexacyanoferrate(III)
solutions of comparable concentrations, 1.0 × 10−2 and 5.0 × 10−3 mol dm−3, yield D
app on the level of 5–6 × 10−6 cm2 s−1. Thus, the dynamics of charge propagation in this sol-gel material is almost as high as in the liquid phase. The residual
water in the silica, along with the pore structure, are important to the overall mechanism of charge transport, which apparently
is limited by physical diffusion rather than electron self-exchange. Under conditions of a solid state voltammetric experiment
which utilizes an ultramicroelectrode, encapsulated iron hexacyanoferrate redox centers seem to be in the dispersed colloidal
state rather than in a form of the rigid polymeric film.
Received: 8 April 1999 / Accepted: 13 August 1999 相似文献
8.
Functionalized polypyrrole films were prepared by incorporation of Fe(CN)6
3− as doping anion during the electropolymerization of pyrrole at a glassy carbon electrode from aqueous solution. The electrochemical
behavior of the Fe(CN)6
3−/Fe(CN)6
4− redox couple in polypyrrole was studied by cyclic voltammetry. An obvious surface redox reaction was observed and dependence
of this reaction on the solution pH was illustrated. The electrocatalytic ability of polypyrrole film with ferrocyanide incorporated
was demonstrated by oxidation of ascorbic acid at the optimized pH of 4 in a glycine buffer. The catalytic effect for mediated
oxidation of ascorbic acid was 300 mV and the bimolecular rate constant determined for surface coverage of 4.5 × 10−8 M cm−2 using rotating disk electrode voltammetry was 86 M−1 s−1. Furthermore, the catalytic oxidation current was linearly dependent on ascorbic acid concentration in the range 5 × 10−4–1.6 × 10−2 M with a correlation coefficient of 0.996. The plot of i
p versus v
1/2 confirms the diffusion nature of the peak current i
p.
Received: 12 April 1999 / Accepted: 25 May 1999 相似文献
9.
The improved generator coordinate Hartree–Fock (GCHF) method is extended to molecular systems. The Griffin–Hill–Wheeler–HF
equations were solved by an integral discretization technique. The method is then implemented with the use of the GAMESS program
and applied to the H2, Li2, and LiH molecules. For these molecules, sequences of basis sets of atom-centred Gaussian-type functions are employed to
explore the accuracy achieved with our approach. For all systems studied, our ground-state HF total energies are better than
those obtained with basis sets generated with the original GCHF method for molecules and larger even-tempered basis sets.
For H2, Li2, and LiH, the differences between our best energies and the corresponding numerical HF results are about 2 × 10−2, 1, and 4 × 10−1 μhartree, respectively. The dipole, quadrupole, and octupole moments at the center of mass and electric field, the electric
field gradient, the electrostatic potential, and the electron density at the nuclei were evaluated and compared with results
reported in the literature.
Received: 4 May 1999 / Accepted: 22 July 1999 / Published online: 2 November 1999 相似文献
10.
Trygve Helgaker Michał Jaszuński Kenneth Ruud Anna Górska 《Theoretical chemistry accounts》1998,99(3):175-182
The convergence of NMR indirect spin-spin coupling constants with the extension of the basis set is analyzed, based on calculations
carried out at the multiconfigurational self-consistent-field level for the HF and H2O systems. For the dominant and difficult Fermi-contact contribution, the standard correlation-consistent basis sets of electronic-structure
theory are not suitable, lacking flexibility in the core region. Improved but not satisfactory convergence of the couplings
is observed when decontracting the s functions of the correlation-consistent cc-pVXZ basis sets for 2≤X≤6. Next, by systematically extending these basis sets with tight s functions, new sets are obtained that are sufficiently flexible for accurate calculations of indirect nuclear spin-spin couplings,
without sacrificing the smooth convergence behavior of the correlation-consistent basis sets.
Received: 22 September 1997 / Accepted: 30 December 1997 相似文献
11.
Ulrich Englich Ingo Prass Karin Ruhlandt-Senge Thorsten Schollmeier Frank Uhlig 《Monatshefte für Chemie / Chemical Monthly》2002,133(7):931-943
Summary. Hydrido substituted stannasilanes of the type or (Z = H, Me, Ph; R, R′ = alkyl, Ph) are accessible by reaction of either alkali metal stannides (MSn(Z)R
2; M = Li, Na) with halogen substituted silanes (; X = F, Cl) or chlorostannanes (R
2SnCl2, Ph3SnCl) and fluorosilanes in the presence of magnesium. Stannasilanes with halogen substituents at the silicon as well as the tin atom are formed by
treatment of the hydrido substituted stannasilanes with CHCl3 or CCl4. The hydrido substituted stannasilanes decompose in contact with air to distannanes and siloxanes or to the linear (
t
Bu2Sn(–O–
t
Bu2Si–OH)2) and cyclic ((–
t
Bu2Sn–O–
i
Pr2Si–O–)2) stannasiloxanes.
Received November 29, 2001. Accepted (revised) January 16, 2002 相似文献
12.
D. A. B. Young 《Colloid and polymer science》2000,278(5):464-468
The persuasive evidence for the role of colloid in the formation of Liesegang rings is nullified by the low diffusion constants
(less than 2 × 10−11 m2 s−1) of sol particles; however, those values were obtained for sols suspended in otherwise homogeneous solutions. The essential
randomness of Brownian motion in such situations is absent in Liesegang experiments, where the large excess of outer electrolyte
diffusing into the gel creates a bias in molecular bombardment resulting in sol particles moving a given distance in fewer
steps, hence in a shorter time. From Einstein's equation (D=x
2/2t) values for D of 2–4 × 10−10 m2 s−1 have been calculated for Liesegang experiments in the literature. It is suggested that such values could well pertain to
sol particles diffusing in the heterogeneous conditions existing in those experiments.
Received: 13 April 1999 Accepted: 16 November 1999 相似文献
13.
N. Hattori H. Hirata H. Okabayashi M. Furusaka C. J. O'Connor R. Zana 《Colloid and polymer science》1999,277(1):95-100
The microstructure of the normal micelles formed by dimeric surfactants with long spacers, [Br−(CH3)2N+(C
m
H2
m
+1)-(CH2)
S
-(C
m
H2
m
+1)N+(CH3)2Br−, m = 10 and s = 8, 10 and 12], has been investigated by small-angle neutron scattering and compared with previously reported results for
micelles of the same dimeric surfactants with shorter spacers (m = 10 and s = 2, 3, 4 and 6). It was found that for dimeric surfactants with long spacers (s = 8 and 10), both micellar growth and variation in shape occur to only a small extent, if at all, compared with dimeric surfactants
with short spacers. However, for the dimeric surfactant with the longest spacer, s = 12, the extent of micellar growth and shape variation is also large. These results are due to the differences in conformation
of dimeric surfactants with short spacers (s = 2–6) compared with that of the surfactants with long spacers (s = 8–12).
Received: 15 June 1998 Accepted: 22 July 1998 相似文献
14.
Contracted Gaussian-type function (CGTF) basis sets are reported for valence p orbitals of the six alkali and alkaline-earth atoms Li, Be, Na, Mg, K, and Ca for molecular applications. These sets are
constructed by Roothaan–Hartree–Fock calculations for the ns → np excited states of atoms, in which both linear and nonlinear parameters of CGTFs are variationally optimized. The present
CGTF sets reproduce well the numerical Hartree–Fock ns → np excitation energies: the largest error is 0.0009 hartrees for Li. New CGTFs are tested with diatomic Li2, Na2, K2, and MH molecules, where M = Li, Be, Na, Mg, K, and Ca, by self-consistent-field (SCF) and multiconfiguration SCF calculations.
The resultant spectroscopic constants compare well with those of more elaborate calculations and are sufficiently close to
experimental values, supporting the efficiency of the present set for the valence p orbitals.
Received: 9 July 1998 / Accepted: 17 September 1998 / Published online: 1 February 1999 相似文献
15.
The protonation constants of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin, H2tpps4−, were determined in water–ethanol and water–methanol mixed solvents, using a combination of spectrophotometric and potentiometric
methods at 20 °C and 0.1 mol⋅dm−3 sodium perchlorate as supporting electrolyte. Two protonation constants, K
1 and K
2, were characterized and were analyzed in various media in terms of the Kamlet, Abboud and Taft (KAT) parameters. Single-parameter
correlations of the protonation constant K
1 versus α (hydrogen-bond donor acidity) and π
* (dipolarity/polarizability) are poor in all solutions, but dual-parameter (α and π
*) correlation represents a significant improvement with regard to the single- and multi-parameter models. However, the single-parameter
correlation of log 10
K
2 in terms of β (hydrogen-bond acceptor basicity) shows a better result than dual- and multi-parameter correlations. Linear correlation is
observed when the experimental log 10
K
1 and log 10
K
2 values are plotted versus the calculated ones when the KAT parameters are considered. To evaluate the protonation constants
of H2tpps4−, the Yasuda-Shedlovsky extrapolation is used to obtain the log 10
K
1 and log 10
K
2 values at zero percent organic solvent. Finally, the results are discussed in terms of the effect of the solvent on protonation. 相似文献
16.
Dao-Lai Fang Bing-Cai Wu Yong Yan Ai-Qin Mao Cui-Hong Zheng 《Journal of Solid State Electrochemistry》2012,16(1):135-142
Mesoporous Mn–Ni oxides with the chemical compositions of Mn1-x
Ni
x
O
δ
(x = 0, 0.2, and 0.4) were prepared by a solid-state reaction route, using manganese sulfate, nickel chloride, and potassium
hydroxide as starting materials. The obtained Mn–Ni oxides, mainly consisting of the phases of α- and γ-MnO2, presented irregular mesoporous agglomerates built from ultra-fine particles. Specific surface area of Mn1–x
Ni
x
O
δ
was 42.8, 59.6, and 84.5 m2 g−1 for x = 0, 0.2, and 0.4, respectively. Electrochemical properties were investigated by cyclic voltammetry and galvanostatic charge/discharge
in 6 mol L−1 KOH electrolyte. Specific capacitances of Mn1-x
Ni
x
O
δ
were 343, 528, and 411 F g−1 at a scan rate of 2 mV s−1 for x = 0, 0.2, and 0.4, respectively, and decreased to 157, 183, and 130 F g−1 with increasing scan rate to 100 mV s−1, respectively. After 500 cycles at a current density of 1.24 A g−1, the symmetrical Mn1–x
Ni
x
O
δ
capacitors delivered specific capacitances of 160, 250, and 132 F g−1 for x = 0, 0.2, and 0.4, respectively, retaining about 82%, 89%, and 75% of their respective initial capacitances. The Mn0.8Ni0.2O
δ
material showed better supercapacitive performance, which was promising for supercapacitor applications. 相似文献
17.
Kirk A. Peterson Angela K. Wilson David E. Woon Thom H. Dunning Jr. 《Theoretical chemistry accounts》1997,97(1-4):251-259
Using systematic sequences of the newly developed correlation consistent core-valence basis sets from cc-pCVDZ through cc-pCV6Z,
the spectroscopic constants of the homonuclear diatomic molecules containing first row atoms, B–F, are calculated both with
and without inclusion of 1s correlation. Internally contracted multireference configuration interaction (IC-MRCI) and singles and doubles coupled cluster
(CCSD) theory with a perturbational estimate of connected triple excitations, CCSD(T), have been investigated. By exploiting
the convergence of the correlation consistent basis sets, complete basis set (CBS) limits have been estimated for total energies,
dissociation energies, equilibrium geometries, and harmonic frequencies. Based on the estimated CBS limits the effects of
1s correlation on D
e
(kcal/mol), r
e
(?), and ω
e
(cm−1) are: +1.1, −0.0070, +10 for B2; +1.5, −0.0040, +13 for C2; +0.9, −0.0020, +9 for N2; +0.3, −0.0020, +6 for O2; and −0.1, −0.0015, +1 for F2.
Received: 20 January 1997 / Accepted: 6 May 1997 相似文献
18.
Gerhard Kahl Elisabeth Schöll-Paschinger Andreas Lang 《Monatshefte für Chemie / Chemical Monthly》2001,132(11):1413-1432
Summary. Compared to the simple one-component case, the phase behaviour of binary liquid mixtures shows an incredibly rich variety
of phenomena. In this contribution we restrict ourselves to so-called binary symmetric mixtures, i.e. where like-particle interactions are equal (Φ11(r) = Φ22(r)), whereas the interactions between unlike fluid particles differ from those of likes ones (Φ11(r) ≠ Φ12(r)). Using both the simple mean spherical approximation and the more sophisticated self-consistent Ornstein-Zernike approximation, we have calculated the structural and thermodynamic properties of such a system and determine phase diagrams,
paying particular attention to the critical behaviour (critical and tricritical points, critical end points). We then study
the thermodynamic properties of the same binary mixture when it is in thermal equilibrium with a disordered porous matrix
which we have realized by a frozen configuration of equally sized particles. We observe – in qualitative agreement with experiment
– that already a minute matrix density is able to lead to drastic changes in the phase behaviour of the fluid. We systematically
investigate the influence of the external system parameters (due to the matrix properties and the fluid–matrix interactions)
and of the internal system parameters (due to the fluid properties) on the phase diagram.
Received June 27, 2001. Accepted July 2, 2001 相似文献
19.
Gerhard Kahl Elisabeth Sch?ll-Paschinger Andreas Lang 《Monatshefte für Chemie / Chemical Monthly》2001,308(5):1413-1432
Compared to the simple one-component case, the phase behaviour of binary liquid mixtures shows an incredibly rich variety of phenomena. In this contribution we restrict ourselves to so-called binary symmetric mixtures, i.e. where like-particle interactions are equal (Φ11(r) = Φ22(r)), whereas the interactions between unlike fluid particles differ from those of likes ones (Φ11(r) ≠ Φ12(r)). Using both the simple mean spherical approximation and the more sophisticated self-consistent Ornstein-Zernike approximation, we have calculated the structural and thermodynamic properties of such a system and determine phase diagrams, paying particular attention to the critical behaviour (critical and tricritical points, critical end points). We then study the thermodynamic properties of the same binary mixture when it is in thermal equilibrium with a disordered porous matrix which we have realized by a frozen configuration of equally sized particles. We observe – in qualitative agreement with experiment – that already a minute matrix density is able to lead to drastic changes in the phase behaviour of the fluid. We systematically investigate the influence of the external system parameters (due to the matrix properties and the fluid–matrix interactions) and of the internal system parameters (due to the fluid properties) on the phase diagram. 相似文献
20.
Ai-Lin Liu Jia-Dong Wang Wei Chen Xing-Hua Xia Yuan-Zhong Chen Xin-Hua Lin 《Journal of Solid State Electrochemistry》2012,16(4):1343-1351
A simple, rapid, sensitive, and accurate method for simultaneous electrochemical determination of procaine and its metabolite
(p-aminobenzoic acid, PABA) for pharmaceutical quality control and pharmacokinetic research was developed using a graphite paste
electrode. The differential pulse voltammetric results revealed that procaine and p-aminobenzoic acid, respectively, showed well-defined anodic oxidation peaks on a carbon paste electrode with a current peak
separation of 155 mV at a scan rate of 100 mV s−1. This well separation of the current peaks for these two compounds in voltammetry enables us to simultaneously determine
them. Good linearity (r > 0.998) between oxidation peak current and concentration was obtained in the range of 5.0 × 10−7–5.0 × 10−5 M for procaine and 5.0 × 10−7–2.0 × 10−5 M for PABA in pH 4.50 acetate buffer solution. The detection limit for both analytes is 5 × 10−8 M (S/N = 3:1). The present voltammetric method has been successfully used to determine trace p-aminobenzoic acid in procaine hydrochloride injection and procaine in plasma with a linear relationship of current to its
concentration ranging from 1.0 × 10−6 to 5.0 × 10−5 M (correlation coefficient of 0.9981) with a low detection limit of 5.0 × 10−7 M (S/N = 3:1). This validated method is promising to the study of pharmacokinetics in Sprague–Dawley rat and rabbit plasma after
an intravenous administration of procaine hydrochloride injection. 相似文献