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61.
The newly adjusted energy-consistent nine-valence-electron pseudopotentials for K to Fr are used to calculate spectroscopic properties for the neutral and positively charged alkali dimers using coupled cluster and density functional theory. For the neutral dimers the static dipole polarizability was calculated. The coupled cluster results are all in excellent agreement with experimental values. The density functionals used can give quite different spectroscopic properties especially for the dipole polarizability, with the Perdew-Wang PW91 functional performing best. 相似文献
62.
63.
Zusammenfassung Es werden molekulare Struktur, Energie des Grundzustandes, Bindungsabstände, Bindungsenergie, Ionisierungsenergie und Protonenaffinität der Siliziumwasserstoffverbindungen SiH
n
, SiH
n
+ und SiHn
– (n=3, 4 oder 5) nach der Einzentrenmethode berechnet.
OCE-calculations on some silicon hydrides of the type SiH n , SiH n + and SiH n –
OCE-Calculations are reported for molecular structures, ground state energies, bond distances, binding energies, ionization potentials and proton affinities of the silicon hydrides SiH n , SiH n + and SiH n – (n=3, 4 or 5).
Résumé Calcul par la méthode monocentrique de la structure moléculaire, de l'énergie de l'état fondamental, des longueurs de liaison, des énergies de liaison, des potentiels d'ionisation et des affinités protoniques pour les hydrures de silicium SiH n , SiH n + et SiH n – (n=3, 4 ou 5).相似文献
64.
This paper deals with the Neumann problem of the pre-Maxwell partial differential equations for a vector field v defined in a region G ? R 3. We approximate its uniquely determined solution (integrability conditions assumed) uniformly on G by explicitly computable particular integrals and linear combinations of vector fields with a “fundamental” sequence of points . 相似文献
65.
The stability of gold phosphine complexes of the form [Au(PH(3))(n)()](+) (n = 1-4) and [AuCl(PH(3))(n)()] (n = 1-3) is analyzed in detail by applying quantum theoretical methods and compared to the coordination behavior of the lighter group 11 elements copper and silver. It is shown that, once [M(PH(3))(2)](+) or [MClPH(3)] (M = Cu, Ag, and Au) is formed, further coordination by PH(3) ligands is relatively weak; i.e., the energy gain to form [M(PH(3))(3)](+) from [M(PH(3))(2)](+) is less than 60 kJ mol(-)(1), and less than 100 kJ mol(-)(1) to form [MCl(PH(3))(2)] from [MClPH(3)]. Relativistic effects in gold significantly influence these factors and reduce the tendency for phosphine coordination beyond two-coordination. This implies that the most favored coordination number for gold is two with either a linear P-Au-P or P-Au-X arrangement (X = a strongly coordinating ligand like Cl(-)). Instead, X-Au-PH(3) units prefer to interact via close Au-Au contacts (aurophilic interactions) keeping the linear structure approximately intact, while the corresponding copper and silver compounds prefer PH(3) coordination to strongly bound M(2)Cl(2) units (M = Cu or Ag) where two chlorine atoms bridge the two metal atoms thus having the formal coordination number of three for copper or silver. 相似文献
66.
The model proteins cytochrome c, myoglobin, ovalbumin, and beta-lactoglobulin were investigated with regard to their adsorption properties on capillaries for electrophoresis. The model compounds were selected to cover a wide range of properties. Cytochrome c is a basic protein (isoelectric point (pI): 9.6; M(r): 11.7 kDa), beta-lactoglobulin is rather acidic (pI: 5.4, M(r): 18.4 kDa), myoglobin was chosen as a neutral reference protein (pI: 6.8-7.4, M(r): 17.8 kDa), and ovalbumin (pI: 5.1, M(r): 45.0 kDa) was selected as a relatively larger analyte. First, the pH dependence of adsorption was investigated for the bare fused silica. A clear correlation to the respective pIs was noted. For myoglobin and ovalbumin, none or negligible adsorption was found above the pI, whereas strong adsorption was noted just below this parameter. Cytochrome c and beta-lactoglobulin already showed distinct adsorption above their pIs. However, none of the proteins showed any significant adsorption more than one pH unit above the pIs. For linear polyacrylamide-coated capillaries, a decreased but not a complete lack of adsorption was observed. Here, pH-dependent adsorption was noted as well. Regeneration of the capillaries by rinsing with buffers containing 200 mM SDS was also investigated. This method was completely successful for myoglobin, but that too for only freshly-adsorbed protein. After a storage time of 24 h and due to the aging of the adsorbate, a sufficient regeneration was no longer possible. 相似文献
67.
Hermann Stoll Gerhard Wagenblast Heinzwerner Preuβ 《Theoretical chemistry accounts》1980,57(2):169-178
Two procedures are discussed for the direct variational optimization of localized molecular orbitals which are expanded in local subsets of the molecular basis set. It is shown that a Newton-Raphson approach is more efficient than an iterative diagonalization scheme. The effect of the basis-set truncation on the quality ofab-initio SCF results is investigated for Be, Li2, HF, H2O, NH3, CH4 and C2H6. 相似文献
68.
Zusammenfassung Die Ionisationskonstanten des Aniliniumions, der drei Chlor- und der drei Nitroaniliniumionen in Methanol bei 2°C, 15°C und 25°C werden mit Hilfe eines spektralphotometrischen Verfahrens bestimmt. Da die Amine im ultravioletten oder im sichtbaren Bereich starke Absorptionsbanden aufweisen, während die Ionenformen fast nicht absorbieren, ist es möglich, durch Messung der Extinktion von Lösungen, in, denen Anilin (substituiertes Anilin) mit Aniliniumion (substituiertem Aniliniumion) im Gleichgewicht steht, die Ionensationskonstante zu ermitteln.Es zeigt sich, daß die Basizität der untersuchten Amine in Methanol größer als in Wasser ist und daß die Einführung eines Chloratoms oder einer Nitrogruppe in den aromatischen Ring eine Abnahme der Basizität verursacht. Dieser Effekt ist bei den Nitroanilinen stärker als bei den Chloranilinen, und bei den o-Verbindungen stärker als bei den m- und p-Verbindungen ausgeprägt.Die Temperaturabhängigkeit der Ionisationskonstanten und damit auch die Ionisationsenthalpien der Aniliniumionen sind in Methanol ebenfalls größer als in Wasser.Mit 2 AbbildungenAus der Diplomarbeit vonW. Melhardt, Technische Hochschule Wien, 1962. 相似文献
69.
70.