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1.
Theoretical study on the atmospheric formation of sulfur trioxide as the primary agent for acid rain
Morteza Vahedpour Moein Goodarzi Nasim Hajari Fariba Nazari 《Structural chemistry》2011,22(4):817-822
The reaction mechanism of SO2 with O3 on the singlet potential energy surface has been investigated theoretically at the G3MP2B3//B3LYP/6-311+G(3df) level of theory.
The reactants are initially associated with adducts IN1(O2S–OOO) and IN2(OS-cyclic O4) in a barrier-less process. Subsequently, these adducts undergo isomerization and dissociation processes to produce cis-OSOO + 3O2, SO3(C
s
) + 3O2 and SO3(D
3h
) + 3O2 products. The SO3(D
3h
) + 3O2 is major product and the cis-OSOO + 3O2 and SO3(C
s
) + 3O2 are minor products. No stable pathway has been found for the formation of trans-OSOO and cyclic-SOOO isomers in the reaction of SO2 + O3. For major product, the rate constant of SO2 + O3 reaction is 2.30 × 10−23 cm3 molecule−1 s−1, at room temperature and atmospheric pressure. 相似文献
2.
Relativistic energy-consistent small-core lanthanide pseudopotentials of the Stuttgart–Bonn variety and extended valence
basis sets have been used for the investigation of the dimers La2 and Lu2. It was found that the ground states for La2 and Lu2 are most likely 1∑
g
+ (σ
g
2π
u
4) and 3∑
g
− (4f
144f
14σ
g
2σ
u
2πu
2), respectively. The molecular constants including error bars were derived from multireference configuration interaction as
well as coupled-cluster calculations, taking into account corrections for atomic spin–orbit splitting as well as possible
basis set superposition errors. The theoretical values for La2 (R
e=2.70±0.03 ?, D
e=2.31±0.13 eV, ωe=186±13 cm−1) show good agreement with the experimental binding energy (D
e=2.52±0.22 eV), but the experimental vibrational constant in an Ar matrix (ωe=236±0.8 cm−1) is significantly higher. For Lu2 the theoretical values (R
e=3.07±0.03 ?, D
e=1.40±0.12 eV, ωe=123±1 cm−1) are in overall excellent agreement with experimental data (D
e=1.43±0.34 eV, ωe=122± 1 cm−1). The electronic structures of La2 and Lu2 are compared to those other lanthanide dimers and trends in the series are discussed.
Received: 25 March 2002 / Accepted: 2 June 2002 / Published online: 21 August 2002 相似文献
3.
Nonempirical methods are used to calculate the geometric parameters, the frequencies of normal vibrations, and thermochemical
characteristics of ions existing in saturated vapors over sodium bromide and iodide: Na2X+, NaX2−, Na3X2+, and Na2X3− (X = Br, I). According to the calculations, Na2X+ and NaX2− triatomic ions have a linear equilibrium configuration of D
∞h
symmetry. Pentaatomic ions can exist in the form of three isomers: linear with D
∞h
symmetry, planar cyclic with C
2v
symmetry, and bipyramidal with D
3h
symmetry. At a temperature of ∼1000 K, Na3X2+ and NaX3− pentaatomic ions are shown to be present in vapor mainly in the form of linear isomers. The energies and enthalpies of ion
molecular reactions with the participation of the above ions are calculated, and the formation enthalpies of the ions are
determined, Δ
f
H
o(0 K): 293±2 kJ/mol (Na2Br+), 354±2 kJ/mol (Na2I+), −536±2 kJ/mol (NaBr2−, −458±2 kJ/mol (NaI2−, 24±5 kJ/mol (Na3Br2+, 143±5 kJ/mol (Na3I2+, −810±5 kJ/mol (Na2Br3−, and −675±5 kJ/mol (Na2I3−. 相似文献
4.
We report an in-situ harvesting technique of electron-hole (e−-h+) carriers (e.g., the defect electrons in the O2 − matrix and the self-trapped holes, Si–O−–Si) generated during sol-gel processing. In the absence of redox species, the e−-h+ centers created during room temperature sol-gel polycondensation steps are quickly annihilated and deactivated. However,
when Cr(VI) ions are pre-dispersed in sol-gel solutions, the ejected electrons can be effectively harvested for the reduction
of Cr(VI) to Cr(III) ions which are encapsulated in the silica gel matrix. The Cr(VI) ions, the possible intermediate oxidation
states of chromium ions such as Cr(V) and/or Cr(IV), and the stable Cr(III)-hole complexes in the sol-gel matrix are investigated
using uv-visible spectroscopy, electron paramagnetic resonance spectroscopy, and cyclic voltammetry. The chemical stability
of Cr(VI) and Cr(III) in sol-gel networks is compared to that in aqueous solutions. The results indicate that the utilization
of e−-h+ carriers generated in the sol-gel can be an effective and selective means for investigating the redox process of Cr(VI) and
encapsulating the stable Cr(III) ions in the confined sol-gel environments. 相似文献
5.
B. N. Plakhutin 《Journal of Structural Chemistry》1997,38(1):1-9
The energy spectrum of the states that appear in structures of icosahedral (I,Ih symmetry with open electronic shells gN (dim g = 4; N = 1–7) is reported. The energies are obtained in terms of integral invariants (reduced matrix elements of electron-electron
interaction) Hk (g, g). The latter are analogs of the Slater-Condon parameters Fk(l,l) for atoms with the lN electronic configuration. A similar representation is proposed for the integrals mm’≨’) of electron-electron interaction
on the 4-fold degenerate g orbitals in the “standard” representation. The relation between the terms of the gN(I,Ih) configuration and the parent states of the orthogonal group O+(4) is discussed.
Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 1, pp. 3–13, January–February, 1997. 相似文献
6.
Quasielastic light scattering measurements are reported for experiments performed on mixtures of gelatin and glutaraldehyde
(GA) in the aqueous phase, where the gelatin concentration was fixed at 5 (w/v) and the GA concentration was varied from 1×10−5 to 1×10−3 (w/v). The dynamic structure factor, S(q,t), was deduced from the measured intensity autocorrelation function, g
2(τ), with appropriate allowance for heterodyning detection in the gel phase. The S(q,t) data could be fitted to S(q,t)=Aexp(−D
f
q
2
t)+Bexp(−t/τc)β, both in the sol (50 and 60 ∘C) and gel states (25 and 40 ∘C). The fast-mode diffusion coefficient, D
f showed almost negligible dependence on the concentration of the crosslinker GA; however, the resultant mesh size, ξ, of the
crosslinked network exhibited strong temperature dependence, ξ∼(0.5−χ)1/5exp(−A/RT) implying shrinkage of the network as the gel phase was approached. The slow-mode relaxation was characterized by the stretched
exponential factor exp(−t/τc)β. β was found to be independent of GA concentration but strongly dependent on the temperature as β=β0+β1
T+β2
T
2. The slow-mode relaxation time, τc, exhibited a maximum GA concentration dependence in the gel phase and at a given temperature we found τc(c)=τ0+τ1
c+τ2
c
2. Our results agree with the predictions of the Zimm model in the gel case but differ significantly for the sol state.
Received: 25 May 1999 /Accepted in revised form: 27 July 1999 相似文献
7.
The geometrical parameters, normal vibration frequencies, and thermochemical characteristics of the Na2Cl+, NaCl
2
−
, Na3Cl
2
+
, and Na2Cl
3
−
ions in saturated vapors over sodium chloride were calculated by the ab initio methods including electron correlation. According to calculations, the Na2Cl+ and NaCl
2
−
triatomic ions have a linear equilibrium D
∞h
configuration. The pentaatomic ions can exist in the form of the D
∞h
linear isomer, C
2v
planar cyclic isomer, or D
3h
bipyramidal isomer. At ∼1000 K the Na3Cl
2
+
and Na2Cl
3
−
ions exist predominantly in the form of the linear isomers. The energies and enthalpies of the ion-molecule reactions involving
the above ions were calculated. The formation enthalpy of the ions Δf
H
0(0 K) was determined: 230 ± 2 kJ/mol (Na2Cl+), −96 ± 4 kJ/mol (Na2Cl
3
−
), −616 ± 2 kJ/mol (NaCl
2
−
), and −935 ± 4 kJ/mol (Na2Cl
3
−
).
Original Russian Text Copyright ? 2007 by T. P. Pogrebnaya, A. M. Pogrebnoi, and L. S. Kudin
__________
Translated from Zhurnal Strukturnoi Khimii, Vol. 48, No. 6, pp. 1053–1061, November–December, 2007. 相似文献
8.
We have obtained interaction dipole moment curves for the rare gas heterodiatoms Rg...Xe (Rg = He, Ne, Ar, and Kr) from conventional ab initio and density functional theory calculations with flexible Gaussian-type basis sets. All methods seem to reproduce fairly similar dipole moment curves for all pairs. Our best values for the interaction dipole moment (at the respective experimental equilibrium separation R
e) were obtained at the coupled-cluster theory with single, double, and perturbatively linked triple excitations level of theory: μint(RgXe)/eα0 = − 0.0025(He), − 0.0047(Ne), − 0.0055(Ar), and − 0.0037(Kr). The same trend (in absolute terms) is observed at the MP2 level of theory for the derivative of the dipole moment at R
e, as (dμint (RgXe)/dR)
e
/e = 0.0043 (He), 0.0082 (Ne), 0.0091 (Ar), and 0.0059 (Kr). Around R
e
, μint(HeXe) ≡ μHeXe varies at the MP2 level of theory as [μHeXe(R) − μHeXe(R
e)]/ea0 = 0.0043(R − R
e) − 0.0033(R − R
e)2 + 0.0018(R − R
e)3 − 0.0005(R − R
e)4. 相似文献
9.
Pasquale Crea Concetta De Stefano Mutsa Kambarami Frank J. Millero Virender K. Sharma 《Journal of solution chemistry》2008,37(9):1245-1259
The protonation constants for oxidized glutathione, H
i−1L(4−i+1)−, K
i
H=[H
i
L(4−i)−]/[H
i−1L(4−i+1)−][H+] i=1,2,…,6 have been measured at 5, 25 and 45 °C as a function of the ionic strength (0.1 to 5.4 mol⋅[kg(H2O)]−1) in NaCl solutions. The effect of ionic strength on the measured protonation constants has been used to determine the thermodynamic
values (K
i
H0) and the enthalpy (ΔH
i
) for the dissociation reaction using the SIT model and Pitzer equations. The SIT (ε) and Pitzer parameters (β
(0), β
(1) and C) for the dissociation products (L4−, HL3−, H2L2−, H3L−, H4L, H5L+, H6L2+) have been determined as a function of temperature. These results can be used to examine the effect of ionic strength and
temperature on glutathione in aqueous solutions with NaCl as the major component (body fluids, seawater and brines). 相似文献
10.
K. K?ppler U. Scheim F. Keidel U. Just 《Fresenius' Journal of Analytical Chemistry》1996,354(1):21-26
Silicone resins can be used as polymeric precursors in the production of ceramic materials. Cohydrolysis of mixtures of trimethylchlorosilane,
methyldichlorosilane, vinylmethyldichlorosilane and phenyltrichlorosilane leads to the formation of especially suitable polysiloxanes,
but also low-molar mass siloxanes are formed as undesired by-products. The structures of these by-products have been elucidated.
Vaporizable components of the matrix have been isolated by distillation, separated using gas chromatography and identified
by mass spectrometry in EI (electron impact ionization) and CI (chemical ionization with isobutane) mode. The EI mass spectra
of the siloxane oligomers with different numbers of Si-H, Si-phenyl and Si-vinyl groups show characteristic fragments like
Me3Si+, ViMe2Si+, Vi2MeSi+, PhMe2Si+, and Ph2MeSi+, which give a first indication to the structure, but generally do not show molecular peaks. A reliable determination of the
molar mass has been possible considering the CI-ions and CI-fragments [M+1]+, [M−1]+, [M−27]+ and [M−77]+, respectively. The compounds M2DPh,OH and M3TPh have been identified as main components of the investigated siloxane mixture. Besides, numerous linear compounds of the type
M2(DH)n(DVi)m and M2TPh(DH)n(DVi)m M as well as cyclic ones of the structure [MTPh(DH)n(DVi)m] with n, m=0–3 have been indicated.
Received: 3 March 1995/Revised: 25 March 1995/Accepted: 3 April 1995 相似文献