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81.
82.
The vertical ionization potentials of bis(-allyl)nickel (see (1) in Fig. 1) are calculated by means of the Green's function approach within a semiempirical INDO extension to the first transition metal series. The computed ionization potentials are in good agreement with an experimentally deduced assignment. In contrast to earlier theoretical and experimental studies, the 7a
u
() level is predicted on top of the levels corresponding to the Ni 3d orbitals. Our approach leads to a complete assignment of the PE spectrum of (1) in the outer valence region. 相似文献
83.
Linear scaling local correlation approach for solving the coupled cluster equations of large systems
A linear scaling local correlation approach is proposed for approximately solving the coupled cluster doubles (CCD) equations of large systems in a basis of orthogonal localized molecular orbitals (LMOs). By restricting double excitations from spatially close occupied LMOs into their associated virtual LMOs, the number of significant excitation amplitudes scales only linearly with molecular size in large molecules. Significant amplitudes are obtained to a very good approximation by solving the CCD equations of various subsystems, each of which is made up of a cluster associated with the orbital indices of a subset of significant amplitudes and the local environmental domain of the cluster. The combined effect of these two approximations leads to a linear scaling algorithm for large systems. By using typical thresholds, which are designed to target an energy accuracy, our numerical calculations for a wide range of molecules using the 6-31G or 6-31G* basis set demonstrate that the present local correlation approach recovers more than 98.5% of the conventional CCD correlation energy. 相似文献
84.
Summary The results of various quantum chemical calculations, the Hartree-Fock (HF) method, the Møller-Plesset perturbation theory (MP2), and the Hartree-Fock-Slater (HFS) method are compared. Atomic charges, dipole moments, topological properties of the electron density distribution and polarizabilities, and first hyperpolarizabilities are calculated. Atomic charges obtained with the HFS method are found to be very close to those calculated with the MP2 method, from which we conclude that the HFS method describes to some extent electron correlation effects. Performing an MP2 calculation after an HF calculation improves the molecular dipole moments considerably, yielding values close to the experimental ones. HFS calculations are computationally less demanding than MP2 and yield comparable results for the electron density distributions, dipole moments and polarizabilities. 相似文献
85.
86.
87.
Crystal structures of new nitronyl nitroxide derivatives 1, 2 and 3 were determined with X‐ray diffraction analysis: 1, monoclinic, C2/c, a = 1.2404(5) nm, b = 0.9730(5) um, c = 2.7049(10) ran, β = 98.189(15)°, V = 3.2315(24) nm3, Z = 8; 2, or‐thorhombic, Pbca, a = 0.61262(2) nm, b = 1.11426(6) nm, c = 2.30543(13) nm, V = 1.57373(13) nm3, Z = 4; 3, monoclinic, P2(1)/n, a=0.64253(4) nm, b=2.55003(17) nm, c = 1.15497(6) nm, β = 95.000(3)°, V = 1.8852(2) nm3, Z = 4. Their magnetic properties were measured with SQUID and analyzed based on their crystal structures with simple singlet‐triplet, modified one dimensional antiferromagnetic chain and modified singlet‐triplet models respectively: 1, J/kb= ?2.5 K; 2, J/kb = 7.8 K, θ = 2.8 K; 3, J/kb = ?0.96 K, θ = 0.21 K. 相似文献
88.
A study was carried out to determine if rotational correlation time of spin-labeled hen egg lysozyme (HEL) interacting with ultrafiltration membranes could be used to infer protein-membrane interaction. Polysulfone and cellulosic membranes, which have notably different adsorption properties, and membranes with varying pore sizes were used in this study. Based on this study, it was determined that the rotational correlation time does reflect variations in protein adsorption and pore plugging on membranes. The rotational correlation times for the highly adsorbent polysulfone (2.82 × 10−8 s) were significantly higher than those obtained from proteins on cellulosic membranes (0.62 × 10−8 s) and from those in solution (0.17 × 10−8 s). Rotational correlation time was also increased due to steric hindrance associated with pore plugging, although it was not as significant as the adsorption effect. This study indicates that the rotational time constant can be used to infer the type of protein-membrane interaction. 相似文献
89.
Assuming the separation of the intermolecular scattering function into the radial and angular parts and using Egelstaffet al’s orientational model for tetrachlorides, the structure of liquid vanadium tetrachloride has been studied. It has been observed
that such a separation is approximate for this liquid and the introduction of a third correction term is required to account
for the molecular structure function. The chlorine-chlorine partial structure and effective angleaveraged intermolecular chlorine-chlorine
potential in the liquid has been evaluated. Without taking the third correction term, introduced to generate theoretically
the molecular structure function, the centre structure function has been obtained in an approximate way from the experimentally
observed molecular structure function and from it the centre radial distribution function, centre direct correlation function
and the angle-averaged vanadium-vanadium effective potential has been evaluated. 相似文献
90.
Jane?Jin John?C.?Achenbach Shiping?ZhuEmail author Yingfu?Li 《Colloid and polymer science》2005,283(11):1197-1205
The influences of polymer-related properties such as molecular weight, charge density, counter ion, and hydrophilic block
on the complexation of polyelectrolytes and a fluorescein-labeled oligonucleotide (ON) were investigated. A series of well-defined
and well-controlled 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) polymers and block copolymers were prepared using living anionic and radical polymerization
methods. Fluorescence measurement was used to reveal the effects of polymer molecular weight, charge density, and counter
ion type on the complexation. PolyDMAEMA samples having double molecular weights of the chosen oligonucleotide gave the optimal
complexation performance. Kinetic studies showed that high-molecular weight/high-charge density polymer samples produced very
stable complexes. The fully charged polyDMAEMA displayed the strongest binding with the ON. These complexes were therefore
less sensitive to the changes in the environment. PolyDMAEMA–DMSQ samples had slightly higher complexation ability than polyDMAEMA–MCQ
(DMSQ: dimethylsulfate quat; MCQ: methylchloride quat). Both poly(DMAEMA-b-HEMA) and poly(DMAEMA–MCQ-b-PEG) block copolymers
showed good complexation ability and steric stability [HEMA: 2-hydroxyethyl methacrylate; PEG: poly(ethylene glycol)]. PEG,
but not HEMA block, enhanced the effectiveness of polyDMAEMA–MCQ binding with the ON. 相似文献