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1.
E. Goering M. Justen J. Geissler U. Rüdiger M. Rabe G. Güntherodt G. Schütz 《Applied Physics A: Materials Science & Processing》2002,74(6):747-753
Highly a-axis-textured CrO2 films have been deposited on Al2O3 (0001) substrates by chemical vapor deposition. CrO2 has been found to have highly a-axis (010)-oriented columnar growth on a Cr2O3 (0001) initial layer. The six-fold surface symmetry of the Cr2O3 initial layer leads to three equivalent in-plane orientations of the a-axis-oriented CrO2 unit cell. We report Cr L2,3 X-ray magnetic circular dichroism data along the surface normal and at 60° off-normal sample orientation. For a 60° sample
alignment, a strong increase of the projected orbital moment could be observed for unoccupied majority t2g states using moment analysis. Therefore, the c axis is identified as the intrinsic magnetic easy axis of CrO2. In addition, a small spin moment and a very strong magnetic dipole term Tz have been found.
Received: 8 January 2002 / Accepted: 8 January 2002 相似文献
2.
Watson MD Jäckel F Severin N Rabe JP Müllen K 《Journal of the American Chemical Society》2004,126(5):1402-1407
Cyclophanes with the largest-to-date polycyclic aromatic hydrocarbon (hexa-peri-hexabenzocoronene, HBC) to be entrained in such a structural motif are reported. The two disks are covalently captured by intermolecular ring-closing olefin metathesis of dienes in good yield. DSC, optical microscopy, and WAXD show the new cyclophanes to self-assemble to thermotropic columnar liquid crystal mesophases similar to monomeric analogues. Solution spectroscopic studies reveal that the two disks within a single unit lie face-to-face, with a small average lateral offset. Self-assembly into two-dimensional crystals at a solid-liquid interface was visualized by STM, and the electrical properties of single molecules were assessed by scanning tunneling spectroscopy revealing a diode-like behavior which is similar to that previously reported for single HBC disks, laying the groundwork for future electrical interrogations of dynamic molecular complexes. 相似文献
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5.
Samorì P Yin X Tchebotareva N Wang Z Pakula T Jäckel F Watson MD Venturini A Müllen K Rabe JP 《Journal of the American Chemical Society》2004,126(11):3567-3575
We report the synthesis and characterization of covalent dyads and multiads of electron acceptors (A) and donors (D), with the purpose of exploiting their nanophase separation behavior toward (a) two-dimensional (2D) surface patterning with well-defined integrated arrays of dissimilar molecular electronic features and (b) bulk self-assembly to noncovalent columnar versions of the so-called "double cable" systems, the likes of which could eventually provide side-by-side percolation pathways for electrons and holes in solar cells. Soluble, alkylated hexa-peri-hexabenzocoronenes (HBCs) bearing tethered anthraquinones (AQs) are shown by scanning tunneling microscopy (STM) to self-assemble at the solution-graphite interface into either defect-rich polycrystalline monolayers or extended 2D crystalline domains, depending on the number of tethered AQs. In the bulk, the thermal stability of the room-temperature HBC columnar phase is increased, which is attributed to the desired nanotriphase separation of HBC columns, insulating alkyl sheaths, and AQ units. Homeotropic alignment (columns normal to surfaces), predicted to be ideal for potential exploitation of such "double cables" in photovoltaic devices, is demonstrated. 相似文献
6.
The molecular structures of novel donor-functionalized terphenyl derivatives of trivalent ytterbium, yttrium, and samarium of composition [DanipYb(mu2-Cl)2(mu3-Cl)Li(THF)]2 (1) and [DanipLn(mu2-Cl)2(mu2-Cl)Li(THF)2]2 (Ln = Y, 2; Ln = Sm, 3) are reported [Danip = 2,6-di(o-anisol)phenyl]. The complexes are obtained from the reaction of equimolar amounts of DanipLi and LnCl3 (Ln = Yb, Y, Sm) in tetrahydrofuran at room temperature in 60% yield. 1-2 toluene crystallizes in the monoclinic space group Ponebar. Crystal data for 1-2 toluene at 203 K: a = 9.7281(9) A; b = 12.7989(12) A; c = 13.4870(12) A; alpha = 91.553(2) degrees; beta = 103.957(2) degrees; gamma = 109.916(2) degrees; V = 1521.2(2) A(3); Z' = 1; D(calcd) = 1.615 g cm(-3); R1 = 3.43%. 2-toluene crystallizes in the monoclinic space group Ponebar. Crystal data for 2-toluene at 203 K: a = 10.4152(10) A; b = 12.5783(12) A; c = 14.4640(14) A; alpha = 69.963(2) degrees; beta = 80.900(2) degrees; gamma = 66.603(2) degrees; V = 1633.3(3) A(3); Z' = 1; D(calcd) = 1.386 g cm(-3); R1 = 4.07%. 3-toluene crystallizes in the monoclinic space group Ponebar. Crystal data for 3-toluene at 203 K: a = 10.3457(8) A; b = 12.5658(10) A; c = 14.4365(11) A; alpha = 70.2250(10) degrees; beta = 81.2820(10) degrees; gamma = 66.8330(10) degrees; V = 1623.3(2) A(3); Z' = 1; D(calcd) = 1.521 g cm(-3); R1 = 3.40%. Complexes 1-3 represent first examples of donor-functionalized terphenyl complexes of the elements ytterbium, yttrium, and samarium, respectively. The molecular structures of 1-3 feature a "constraint geometry" type arrangement of the Danip ligand at the lanthanide atom. The complexes reported are dimeric and composed of lithium chloride bridged DanipLnCl(2) moieties (Ln = Yb, Y, Sm), stabilized through additional coordination of two methoxy functions to the lanthanide atom. 相似文献
7.
Rappe AM Rabe KM Kaxiras E Joannopoulos JD 《Physical review. B, Condensed matter》1991,44(23):13175-13176
8.
Reactions of Phosphorus(Arsenic)chalcogenides with Phosphorus(Arsenic)triiodide The specific heats and enthalpies of melting of the tetraphosphorustrithio(seleno)-diiodides have been determined. For the preparation of β-P4S3I2 a new mthod by reacting P4S3 with PI3 in CS2 solution was found. Experiments to prepare compounds of the type As4S3I2 by the classical methods for the preparation of the resp. phosphorus compounds failed. The reaction of As4S3 with AsI3 leads to the formation of As4S4. The other sulphides of the As? S system As2S3 and As4S4 react with AsI3 to AsSI, however, in the reaction of As4S4 the addition of S is necessary. 相似文献
9.
The molecular structures of terphenyl derivatives of trivalent ytterbium, thulium, and yttrium of general composition DnpLnCl(2)(THF)(2) [Dnp = 2,6-di(1-naphthyl)phenyl] are reported. The complexes (Ln = Yb: 1; Ln = Tm: 2; Ln = Y: 3) are synthesized by reaction of 1 equiv of DnpLi with 1 equiv of LnCl(3) (Ln = Yb, Tm, or Y) in tetrahydrofuran at room temperature in 50% yield. Attempts to prepare a Dnp scandium compound gave heterobimetallic [(THF)(3)Sc(2)OCl(5)Li(THF)](2) (4) in low yield. 1 crystallizes in the monoclinic space group C2/c. Crystal data for 1 at 203 K: a = 14.333(3) A, b = 16.353(3) A, c = 12.427(2) A, beta = 91.021(4) degrees, Z = 4, D(calcd) = 1.637 g cm(-3), R(1) = 4.44%. 2 crystallizes in the monoclinic space group C2/c. Crystal data for 2 at 203 K: a = 14.333(1) A, b = 16.374(2) A, c = 12.404(1) A, beta = 90.934(2) degrees, Z = 4, D(calcd) = 1.628 g cm(-3), R(1) = 3.00%. 3 crystallizes in the monoclinic space group C2/c. Crystal data for 3 at 203 K: a = 14.348(3) A, b = 16.476(3) A, c = 12.356(2) A, beta = 90.987(4) degrees, Z = 4, D(calcd) = 1.441 g cm(-3), R(1) = 5.62%. 4 crystallizes in the monoclinic space group P2(1)/n. Crystal data for 4 at 203 K: a = 11.0975(9) A, b = 11.0976(9) A, c = 21.3305(18) A, beta = 94.718(2) degrees, Z = 2, D(calcd) = 1.051 g cm(-3), R(1) = 3.45%. Complexes 1-3 represent examples of novel chiral (racemic) organometallic complexes of the lanthanide elements ytterbium and thulium and the group 3 element yttrium, respectively. The molecular structures of monomeric 1-3 exhibit distorted trigonal-bipyramidal coordination environments at the metal center, with the two oxygen atoms of the tetrahydrofuran ligands occupying the axial positions of a trigonal-bipyramidal coordination polyeder. The molecular structure of the scandium compound 4 shows a complex polynuclear heterobimetallic arrangement. 相似文献