Stochastic effects at ripple formation processes in anisotropic systems with multiplicative noise

We study pattern formation processes in anisotropic system governed by the Kuramoto-Sivashinsky equation with multiplicative noise as a generalization of the Bradley-Harper model for ripple formation induced by ion bombardment. For both linear and nonlinear systems we study noise induced effects at ripple formation and discuss scaling behavior of the surface growth and roughness characteristics. It was found that the secondary parameters of the ion beam (beam profile and variations of an incidence angle) can crucially change the topology of patterns and the corresponding dynamics

Electric Field Gradients in S-, P-, and D-Metal Diborides and the Effect of Pressure on the Band Structure and T\u3csub\u3ec\u3c/sub\u3e in MgB₂

Results of full-potential linear muffin-tin orbital generalized gradient approximation calculations of the band structure and boron electric field gradients (EFG\u27s) for the new medium-Tc superconductor MgB2 and related diborides MB2, M = Be, Al, Sc, Ti, V, Cr, Mo, and Ta are reported. The boron EFG variations are found to be related to specific features of their band structure and particularly to the M-B hybridization. The strong charge anisotropy at the B site in MgB2 is completely defined by the valence electrons - a property which sets MgB2 apart from other diborides. The boron EFG in MgB2 is weakly dependent on applied pressure: the B p-electron anisotropy increases with pressure, but it is partly compensated by the increase of core charge asymmetry. The concentration of holes in bonding or bands is found to decrease slightly from 0.067 to 0.062 holes/B under a pressure of 10 GPa. Despite a small decrease of N(EF), the Hopfield parameter increases with pressure and we believe that the main reason for the reduction under pressure of the superconducting transition temperature Tc is the strong pressure dependence of phonon frequencies, which is sufficient to compensate for the electronic effects

Bifunctional Reactivity of Amidoximes Observed upon Nucleophilic Addition to Metal-Activated Nitriles

Treatment of the aromatic nitrile complexes <i>trans</i>-[PtCl₂(RC₆H₄CN)₂] (R = <i>p</i>-CF₃ <b>NC1</b>, H <b>NC2</b>, <i>o</i>-Cl <b>NC3</b>) with the aryl amidoximes <i>p</i>-R′C₆H₄C­(NH₂)NOH (R′ = Me <b>AO1</b>, H <b>AO2</b>, Br <b>AO3</b>, CF₃ <b>AO4</b>, NO₂ <b>AO5</b>) in all combinations, followed by addition of 1 equiv of AgOTf and then 5 equiv of Et₃N, leads to the chelates [PtCl­{H<u>N</u>C­(RC₆H₄)­O<u>N</u>C­(C₆H₄R′-<i>p</i>)­NC­(RC₆H₄)<u>N</u>H}] (<b>1</b>–<b>15</b>; 15 examples; yields 71–88% after column chromatography) derived from the platinum­(II)-mediated coupling between metal-activated nitriles and amidoximes. The mechanism of this reaction was studied experimentally by trapping and identification of the reaction intermediates, and it was also investigated theoretically at the DFT level of theory. The combined experimental and theoretical results indicate that the coupling with the nitrile ligands involves both the HON and monodeprotonated NH₂ groups of the amidoximes, whereas in the absence of the base, the NH₂ functionality is inactive toward the coupling. The observed reaction represents the first example of bifunctional nucleophilic behavior of amidoximes. The complexes <b>1</b>–<b>16</b> were characterized by elemental analyses (C, H, N), high-resolution ESI⁺-MS, FTIR, and ¹H NMR techniques, whereas unstable <b>17</b> was characterized by HRESI⁺-MS and FTIR. In addition, <b>8</b>·C₄H₈O₂, <b>12</b>, and <b>16</b>·CHCl₃ were studied by single-crystal X-ray diffraction