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1.
The photodetachment spectra of (H2O) n =2?69/? and (NH3) n =41?1100/? have been recorded, and vertical detachment energies (VDEs) were obtained from the spectra. For both systems, the cluster anion VDEs increase smoothly with increasing sizes and most species plot linearly withn ?1/3, extrapolating to a VDE (n=∞) value which is very close to the photoelectric threshold energy for the corresponding condensed phase solvated electron system. The linear extrapolation of this data to the analogous condensed phase property suggests that these cluster anions are gas phase counterparts to solvated electrons, i.e. they are embryonic forms of hydrated and ammoniated electrons which mature with increasing cluster size toward condensed phase solvated electrons.  相似文献   

2.
B-Flourosubstituted cyclopentadienyldicarbollylcobalt and -iron were synthesized. Electrochemical studies of iron 5-C5H5-3,1,2-FeC2B9H11–n F n (n = 2–4) complexes were carried out.19F NMR, UV, and IR spectra of the cobalt and iron complexes were obtained.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2984–2989, December, 1996,  相似文献   

3.
Anionic tetrahydrofuran clusters (THF)(n) (-) (1≤n≤100) are studied with photoelectron imaging as gas-phase precursors for electrons solvated in THF. Photoelectron spectra of clusters up to n=5 show two peaks, one of which is attributed to a solvated open chain radical anion and the other to the closed THF ring. At n=6, the spectra change shape abruptly, which become more characteristic of (THF)(n) (-) clusters containing solvated electrons. From n=6-100, the vertical detachment energies (VDEs) of these solvated electron clusters increase from 1.96 to 2.71 eV, scaling linearly with n(-1/3). For fully deuterated (THF-d8)(n) (-) clusters, the apparent transition to a solvated electron cluster is delayed to n=11. Extrapolation of the VDEs to infinite cluster size yields a value of 3.10 eV for the bulk photoelectric threshold. The relatively large VDEs at onset and small stabilization with increasing cluster size compared to other solvated electron clusters may reflect the tendency of the bulk solvent to form preexisting voids that can readily solvate a free electron.  相似文献   

4.
Electronic properties of silicon-fluorine and germanium-fluorine cluster anions (SinF m ? n = 1–9, m = 1–3, GenF m ? ; n =1–9, m = 1–3) were investigated by photoelectron spectroscopy using a magnetic-bottle type electron spectrometer. The binary cluster anions were generated by a laser vaporization of a silicon/germanium rod in an He carrier gas mixed with a small amount of SiF4 or F2 gas. Comparison between photoelectron spectra of SinF?/GenF? and Sin /Gen (n = 4–9) gives the insight that the doped F atom can remove one electron from the corresponding Sin n ? /Ge n ? cluster without any serious rearrangement of Sin/Gen framework, because only the first peak of Si n ? /Ge n ? , corresponding singly occupied molecular orbital (SOMO), disappears and other successive spectral features are unchanged with the F atom doping  相似文献   

5.
Motivated by recent progress in the mass spectroscopy of the elementary reaction of alkali metals and water dispersed in ultracold helium nanodroplets (S. Müller et al., Phys. Rev. Lett., 2009, 102, 183401.), we investigate the properties of pure and mixed Cs clusters and cluster ions, Cs(l)H(m)O(n)(0/+), from a quantum chemical perspective. The presence of Cs atoms requires a careful choice of the methodology, which we have tested for small molecules for which experimental results were available. With the thus selected density functional, pseudopotential and basis set, we compute the geometry, the ionization potentials and the atomization energy, enabling a proper estimate of the energetics of cluster fragmentation upon photoionization. Based upon these calculations, we are able to construct a fragmentation tree that rationalizes the origin of all peaks observed in the experimental mass spectrum. Infrared spectra are computed, and we introduce a simple mixed quantum-classical model that essentially reproduces the cluster geometries.  相似文献   

6.
The molecular structures, electron affinities, and dissociation energies of neutral Si n Li (n = 2–10) species and their anions have been studied by the B3LYP and the BPW91 methods in conjunction with a DZP++ basis set. The geometries have been fully optimized with each of the proposed methods. The ground state structure of neutral Si n Li keeps the corresponding Si n framework unchanged. For anion, the corresponding Si n (or ${{\rm Si}_{n}^{-}}$ ) framework changes largely when n ≥ 7. To evaluate the stability of the resulting anions we have calculated the adiabatic electron affinity (EAad), the vertical electron affinity (EAvert), and the vertical detachment energy (VDE). The dissociating energies of Li from the lowest energy structures of neutral Si n Li and their anions are calculated to examine relative stabilities.  相似文献   

7.
Low-energy collision induced dissociation has been used to investigate the structure and stability of microsolvated clusters of the prototypical, aprotic multiply charged anion, Pt(CN)(4)(2-), i.e. Pt(CN)(4)(2-)·(H(2)O)(n) n = 1-4, Pt(CN)(4)(2-)·(MeCN)(m) m =1, 2, and Pt(CN)(4)(2-)·(H(2)O)(3)·MeCN. For all of the systems studied, the lowest energy fragmentation pathway was found to correspond to decay of the cluster with loss of the entire solvent ensemble. No sequential solvent evaporation was observed. These observations suggest that the Pt(CN)(4)(2-) solvent clusters studied here form hydrogen-bonded "surface solvated" structures. Electronic structure calculations are presented to support the experimental results. In addition, the detailed fragmentation patterns observed are interpreted with reference to the differential solvation of the ionic fragmentation and electron detachment potential energy surfaces of the core Pt(CN)(4)(2-) dianion. The results described represent some of the first experiments to probe the microsolvation of this important class of multiply charged anions.  相似文献   

8.
《Chemical physics》1987,118(2):273-284
Ab initio and pseudopotential (PP) calculations on the SiHn radicals and their anions show close agreements at all levels of theory. The calculated dipole moment for SiH of about −0.1 D is in excellent agreement with recent studies at comparable levels of theory and strongly queries the large experimental estimate of more than 1 D. The PP CI(SD) calculations on the 1A1, 3B1, and 2B1 states of SiH2 and SiH2 allow a consistent interpretation of the photodetachment spectrum of the anionic ground state. At the same level of theory the classical inversion barriers of SiH3 and SiH3 are found to be 5.39 and 25.07 kcal/mol, which is in perfect agreement with the experimental estimates. All calculations document a satisfactory performance of the effective potential at all levels of theory. At the highest level of theory the calculated electron affinities are at variance with the experimentally determined values by only 0.15 eV or even less.  相似文献   

9.
The structures and properties of Al n , Al n + , Al n (n=1,5) clusters have been investigated by using the Linear Combination of Gaussian Type Orbitals (LCGTO) method, considering Local (LSD) and Non Local (NLSD) Spin Density Approximations and employing a Model Core Potential (MCP) that allows the explicit treatment of 3s 2 3p 1 valence electrons. For each system different geometrical structures and electronic states have been considered. For Al3, Al 3 + , Al 3 the most stable geometry proved to be the equilateral triangle (D 3h ). Al4 and Al 4 + prefer the rhombus (D 2h ) structure, while the corresponding anion prefers the square (D 4h ) one. The trapezoidal form (C 2v ) is the most stable isomer for Al5, Al 5 + and Al 5 clusters. The analysis of vibrational frequencies shows that these structures are minima in the potential energy surface. The binding energies (D e), the adiabatic ionization potentials (IP) and electron affinities (EA), the chemical potentials or absolute hardnesses () and electronegativities () have been computed. Results are in good agreement with the available experimental data and the previous high level theoretical computations.  相似文献   

10.
Structural Chemistry - In this work, the stability and electronic properties of the Ru-doped germanium clusters were investigated with DFT calculations at the TPSS/SDD level. The adsorption of the...  相似文献   

11.
Using density functional theory (DFT), we have systematically calculated the equilibrium geometries, electronic structure, and electron detachment energies of Al(BH(4))(n=1→4) and Al(BF(4))(n=1→4) at the B3LYP/6-311+G(2d,p) level of theory. The electron affinities of Al(BH(4))(n) not only exhibit odd-even alternation, just as seen in (BH(4))(n), but also, for n = 3 and 4, show a remarkable behavior: whereas the electron affinities of BH(3) and BH(4) are, respectively, 0.06 and 3.17 eV, those of Al(BH(4))(3) and Al(BH(4))(4) are 0.71 and 5.56 eV. Results where H is replaced by F are also very different. The electron affinities of BF(3) and BF(4) are, respectively, -0.44 and +6.86 eV, and those of Al(BF(4))(3) and Al(BF(4))(4) are 1.82 and 8.86 eV. The results demonstrate not only marked difference when H is replaced by F but also substantially enhanced electron affinities by almost 2 eV when BH(4) and BF(4) units are allowed decorate a metal atom, confirming the recently observed hyperhalogen behavior of superhalogen building blocks.  相似文献   

12.
The phase composition of Y x Ba1?x CuO y (x = 0.29?0.40) samples annealed in air (at 930?C990°C) and in an oxygen atmosphere (450?C800°C, P(O2) = 101 kPa) was studied by X-ray powder diffraction, chemical analysis, electron diffraction, and elemental analysis in a transmission electron microscope. A considerable cation nonstoichiometry was discovered in particles having the tetragonal and orthorhombic structures of YBa2Cu3O6 + ??. The variation range of particle compositions comprises matrix oxides of the Ba m Cu m + n O y series with (Ba: Cu) 3: 5, 5: 8, 2: 3, and 5: 7, which in the presence of yttrium form the Y n Ba m Cu m + n O y series. Tetragonal oxides Y2Ba3Cu5O y (235), Y3Ba5Cu8O y (358), YBa2Cu3O y (123), and Y2Ba5Cu7O y (257) are formed at the primary synthesis step in air and are preserved in an orthorhombic structure during short-term (1 h) oxygen annealing. Most particles of the 3: 5 and 5: 8 oxides are undersaturated with yttrium relative to the stoichiometry of the Y n Ba m Cu m + n O y series, those of the 2: 3 oxide correspond to this stoichiometry, and those of the 5: 7 oxide are supersaturated with yttrium over the stoichiometry. A trend is observed for the fractions of these oxides to change during long-term (5?C51 h) annealing in an oxygen atmosphere at 450°C and to the alternation of the dominant role of one of the four phases with the superconducting transition temperature T c = 82, 85, 86, and 91 K. Each orthorhombic oxide undergoes structural transformations during oxygen annealing with a change in T c. The coexistence of these oxides in the form of nanometer-sized domains does not allow their individual superstructures to be recognized.  相似文献   

13.
An efficient mixed molecular dynamics/quantum mechanics model has been applied to the water cluster system. The use of the MP2 method and correlation consistent basis sets, with appropriate correction for BSSE, allows for the accurate calculation of electronic and free energies for the formation of clusters of 2-10 water molecules. This approach reveals new low energy conformers for (H(2)O)(n=7,9,10). The water heptamer conformers comprise five different structural motifs ranging from a three-dimensional prism to a quasi-planar book structure. A prism-like structure is favored energetically at low temperatures, but a chair-like structure is the global Gibbs free energy minimum past 200 K. The water nonamers exhibit less complexity with all the low energy structures shaped like a prism. The decamer has 30 conformers that are within 2 kcal/mol of the Gibbs free energy minimum structure at 298 K. These structures are categorized into four conformer classes, and a pentagonal prism is the most stable structure from 0 to 320 K. Results can be used as benchmark values for empirical water models and density functionals, and the method can be applied to larger water clusters.  相似文献   

14.
We have assessed the ability of 52 methods including 15 multicoefficient correlation methods (MCCMs), two complete basis set (CBS) methods, second-order M?ller-Plesset perturbation theory (MP2) with 5 basis sets, the popular B3LYP hybrid functional with 6 basis sets, and 24 combinations of local density functional and basis set to accurately reproduce reaction energies obtained at the Weizmann-1 level of theory for hydronium, hydroxide, and pure water clusters. The three best methods overall are BMC-CCSD, G3SX(MP3), and M06-L/aug-cc-pVTZ. If only microsolvated ion data is included, M06-L/aug-cc-pVTZ is the best method; it has errors only half as large as the other density functionals. The deviations between the three best performing methods are larger for the larger hydronium- and hydroxide-containing clusters, despite a decrease in the average reaction energy, making it impossible to determine which of the three methods is overall the best, so they might be ranked in order of increasing cost, with BMC-CCSD least expensive, followed by M06-L/aug-cc-pVTZ. However, the cost for M06-L will increase more slowly as cluster size increases. This study shows that the M06-L functional is very promising for condensed-phase simulations of the transport of hydronium and hydroxide ions in aqueous solution.  相似文献   

15.
1H, 13C and 31P NMR data of the compounds {(C2H5)2N}nPX3−n, (X = Cl, C2H5; n = 0, 1, 2, 3) are reported. While the 1H and 13C resonances from the PEt moiety rather follow the electron-withdrawing effect of the NEt2 substituent, 1H and 13C chemical shift data from the NEt2 moiety reveal a quite important shift contribution originating from sterically induced polarization of the CH bonds . 31P chemical shift data are interpreted in terms of inductive effects but the anomalous diamagnetic shift deviation from linearity for X = Cl suggests a minor contribution from
multiple bonding. The general trend observed in the 31P-couplings is quite straightforward and can be qualitatively explained by Bent's rule.  相似文献   

16.
The complexation energies of H3BNHnCl3−n (n= 3-0) complexes and the proton affinities of NHnCl3−n compounds have been computed at the G2(MP2) level of theory. G2(MP2) results show that the successive chlorine substitution on the ammonia decreases both the basicity of the NHnCl3−n ligands and the stability of H3BNHnCl3−n complexes. The findings are interpreted in terms of the rehybridisation of the nitrogen lone-pair orbital. The NBO partitioning scheme shows that the variation of the N-H and N-Cl bond lengths, upon complexation, is due to variation of “s” character in these bonds.   相似文献   

17.
Members of the systems Co1−xRhxS2 (0 ≤ x ≤ 0.6) were prepared, and their crystallographic and magnetic properties studied. The observed ferromagnetic moments for compositions where x ≤ 0.2 indicate a ferromagnetic alignment between Co(3d7) and Rh(4d7) electrons. This is the first observation of localized behavior of 4d electrons in the pyrite structure. Members of the systems Co1−xRuxS2 (0 ≤ x ≤ 1) and Rh1−xRuxS2 (0.5 ≤ x ≤ 1) were also prepared and their crystallographic and magnetic properties studied. From comparison with the Co1−xRhxS2 system, it appears that the 4d electrons of Rh(4d7) are localized in the presence of Co(3d7) but are delocalized in the presence of Ru(4d6). The magnetic susceptibility of the Co1−xRuxS2 system is sensitive to the homogeneity of the products and indicates that Ru(4d6) behaves as a diamagnetic ion.  相似文献   

18.
 The possible geometrical structures and relative stability of (SiS2) n (n=1–6) silicon–sulfur clusters are explored by means of density functional theory quantum chemical calculations. The effects of polarization functions and electron correlation are included in these calculations. The electronic structures and vibrational spectra of the most stable geometrical structures of (SiS2) n are analyzed by the same method. As a result, the regularity of the (SiS2) n cluster growth is obtained, and the calculation may used for predicting the formation mechanism of the (SiS2) n cluster. Received: 17 November 1999 / Accepted: 3 November 2000 / Published online: 3 May 2001  相似文献   

19.
The optimized geometries, adiabatic electron affinities, and IR-active vibrational frequencies have been predicted for the long linear carbon chains HC(2n)H. The B3LYP density functional combined with the DZP basis set was used in this theoretical study. The computed physical properties are discussed. The predicted electron affinities form a remarkably regular sequence: 1.78 (HC(12)H), 2.08 (HC(14)H), 2.32 (HC(16)H), 2.53 (HC(18)H), 2.69 (HC(20)H), 2.83 (HC(22)H), and 2.95 eV (HC(24)H). The predicted structures display an alternating triple and very short single bond pattern, with the degree of bond alternation significantly less for the radical anions.  相似文献   

20.
The binding of SO2 on gas-phase gold cluster anions, AuN, and their hydroxide counterparts, AuNOH, have been studied using density functional theory combined with flow reactor/time-of-flight mass spectrometry techniques. SO2 is adsorbed on all of the AuN and AuNOH clusters (N = 1-8) and the hydroxide clusters are more active than the bare anionic clusters. Successive additions of SO2 molecules (up to four) have been analyzed. In all cases, anionic clusters are shown to bind multiple SO2 molecules. Theoretical analyses are in agreement with the experimental results, showing that the addition of more than one molecule is thermodynamically favorable. Larger clusters do not necessarily absorb more molecules, as different SO2 binding motifs on these clusters are present. These results provide important insight for the potential use of these anionic clusters as SO2 hunters.  相似文献   

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