排序方式: 共有61条查询结果,搜索用时 250 毫秒
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Fractionation effects and the formation of structured domains are investigated in polydisperse systems of attractive spherocylinders with the help of Monte Carlo simulations. For sufficiently high attractive interaction strength and pressure, the large rods in the system aggregate and form a highly ordered hexatic monolayer that coexists with an isotropic fluid of smaller rods. Fractionation diminishes with decreasing interaction strength but is still observed for hard rod systems, in which the large rods form a nematic droplet rather than a monolayer. Results for polydisperse systems are accompanied by phase diagrams for monodisperse systems of attractive spherocylinders. Here, the phase behavior is shown as a function of rod length and pressure. 相似文献
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Coropceanu V Malagoli M da Silva Filho DA Gruhn NE Bill TG Brédas JL 《Physical review letters》2002,89(27):275503
The hole-vibrational coupling is reported for anthracene, tetracene, and pentacene on the basis of a joint experimental and theoretical study of ionization spectra using high-resolution gas-phase photoelectron spectroscopy and first-principles correlated quantum-mechanical calculations. The hole-vibrational coupling is found to be significantly smaller than the electron-vibrational coupling in the case of these oligomers; however, both quantities are predicted to converge to the same value when increasing the chain length. 相似文献
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The He I photoelectron spectra of benzo-2,1,3-thia-, selena-, and telluradiazole were measured, and the observed ionization bands were assigned by comparison with the results of DFT calculations. Whereas the B3LYP exchange-correlation functional provided orbital energies that permitted a preliminary assignment by application of Koopman's theorem, a more-accurate interpretation was established by calculation of the vertical ionization energies with the PW91 functional and analysis of the correlation of energy levels along the homologous series. This strategy clarified earlier disagreements in the assignment of the spectrum of benzo-2,1,3-thiadiazole. 相似文献
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The adhesion of fluid vesicles at chemically structured substrates is studied theoretically via Monte Carlo simulations. The
substrate surface is planar and repels the vesicle membrane apart from a single surface domain γ , which strongly attracts
this membrane. If the vesicle is larger than the attractive γ domain, the spreading of the vesicle onto the substrate is restricted
by the size of this surface domain. Once the contact line of the adhering vesicle has reached the boundaries of the γ domain,
further deflation of the vesicle leads to a regime of low membrane tension with pronounced shape fluctuations, which are now
governed by the bending rigidity. For a circular γ domain and a small bending rigidity, the membrane oscillates strongly around
an average spherical cap shape. If such a vesicle is deflated, the contact area increases or decreases with increasing osmotic
pressure, depending on the relative size of the vesicle and the circular γ domain. The lateral localization of the vesicle's
center of mass by such a domain is optimal for a certain domain radius, which is found to be rather independent of adhesion
strength and bending rigidity. For vesicles adhering to stripe-shaped surface domains, the width of the contact area perpendicular
to the stripe varies nonmonotonically with the adhesion strength. 相似文献
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We show that in the metallic magnetic superlattices, along with the bilinear RKKY-like exchange, there is significant biquadratic contribution arising from intrinsic and fluctuational mechanisms. Within the phenomenological approach, we postulate a particular form of free energy density functional and study the thermodynamic behaviour of the system under consideration. The model permits a transparent interpretation of the phase transitions, observed in metallic multilayers, with multiple oscillation periods and biquadratic exchange effects taken into account. 相似文献
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Glass RS Gruhn NE Lorance E Singh MS Stessman NY Zakai UI 《Inorganic chemistry》2005,44(16):5728-5737
Stannylated dinuclear iron dithiolates (mu-SSnMe(2)CH(2)S)[Fe(CO)(3)](2), (mu-SCH(2)SnMe(2)CH(2)S) [Fe(CO)(3)](2), and (mu-SCH(2)SnMe(3))(2)[Fe(CO)(3)](2), which are structurally similar to the active site of iron-only hydrogenase, were synthesized and studied by gas-phase photoelectron spectroscopy. The orbital origins of ionizations were assigned by comparison of He I and He II photoelectron spectra and with the aid of hybrid density functional electronic structure calculations. Stannylation lowers the ionization energy of sulfur lone pair orbitals in these systems owing to a geometry-dependent interaction. The Fe-Fe sigma bond, which is the HOMO in all these systems, is also substantially destabilized by stannylation due to a previously unrecognized geometry-dependent interaction between axial sulfur lone pair orbitals and the Fe-Fe sigma bond. Since cleaving the Fe-Fe sigma bond is a key step in the mechanism of action of iron-only hydrogenase, these newly recognized geometry-dependent interactions may be utilized in designing biologically inspired hydrogenase catalysts. 相似文献
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Gruhn NE da Silva Filho DA Bill TG Malagoli M Coropceanu V Kahn A Brédas JL 《Journal of the American Chemical Society》2002,124(27):7918-7919
The reorganization energy in pentacene is reported on the basis of a joint experimental and theoretical study of pentacene ionization using high-resolution gas-phase photoelectron spectroscopy, semiempirical intermediate neglect of differential overlap calculations, and first-principles correlated quantum-mechanical calculations at MP2 and density functional theory levels. The reorganization energy upon positive ionization of pentacene is determined both experimentally and theoretically to be remarkably low. This is one key element that allows one to rationalize the extremely high hole mobilities recently measured in pentacene single crystals. 相似文献