Basal Edge Research Articles

Nonstoichiometric Dislocation Cores in α-Alumina

Little is known about dislocation core structures in oxides, despite their central importance in controlling electrical, optical, and mechanical properties. It has often been assumed, on the basis of charge considerations, that a nonstoichiometric core structure could not exist. We report atomic-resolution images that directly resolve the cation and anion sublattices in alumina (alpha-Al2O3). A dissociated basal edge dislocation is seen to consist of two cores; an aluminum column terminates one partial, and an oxygen column terminates the second partial. Each partial core is locally nonstoichiometric due to the excess of aluminum or oxygen at the core. The implication for mechanical properties is that the mobile high-temperature dislocation core structure consists of two closely spaced partial dislocations. For basal slip to occur, synchronized motion of the partials on adjacent planes is required.

The influence of explant orientation and contact with the medium on the pathway of shoot regeneration in vitro in epicotyl cuttings of Troyer citrange

The effect of orientation as regards to gravity, and that of contact with the medium of culture, on shoot regeneration at the cut edges of epicotyl explants of Troyer citrange (Citrus sinensis (L.) Osbeck×Poncirus trifoliata (L.) Raf.) have been separated. The shoot regeneration pathway was not affected by the orientation of the explants as regards to gravity, and was determined by explant polarity and the contact with the culture medium. At the apical edge of the explants, the contact with the medium shifted the pathway of shoot regeneration from a direct one to an indirect one, with formation of a callus. This callus formation was cytokinin-dependent, but the change in the pathway of organogenesis was not caused by the increase in cytokinin availability resulting from the contact with the medium. In contact with the media, regeneration at the basal edge of the explants occurred through an indirect pathway after callus formation. No regeneration occurred, at the basal edge, if the contact with the media was prevented. The orientation of the explants as regards to gravity affected shoot formation through the direct pathway of organogenesis. The number of buds differentiated, and that of growing shoots increased when the orientation of the explants departed from the vertical upright position.

Addition of Alkynes to High Nuclearity Platinum–Ruthenium Carbonyl Cluster Complexes

The reactions of the mixed metal cluster complexes PtRu5(CO)16(μ6-C)[Pt(PBu \(^{{\rm t}}_3\))], 5 and PtRu5(CO)16(μ6-C)[Pt(PBu \(^{\rm t}_{3})\)]2, 6 with selected alkynes have been investigated. Compound 5 adds one and two equivalents of PhC2H to yield the new compounds PtRu5(CO)15(μ6-C)(μ3-PhC2H)[Pt(PBu \(^{{\rm t}}_3\))], 8 and PtRu5(CO) \(_{13}(\mu_6\)-C)( \(\mu_3\)-PhC2H)2[Pt(PBu \(^{{\rm t}}_3\))], 9 at 40 and 68°C, respectively. Compound 6 was found to react with PhC2H at 40°C to yield the new compound PtRu5(CO) \(_{16}(\mu_{6}\)-C)( \(\mu_3\)-PhC2H)[Pt(PBu \(^{{\rm t}}_3\))]2, 10. The reaction of 6 with PhC2Ph at 97°C yielded the new compound PtRu5(CO) \(_{12}(\mu_{6}\)-C)( \(\mu_3\)-PhC2Ph)2[Pt(PBu \(^{{\rm t}}_{3}\))]2, 11. All products were characterized crystallographically by single crystal X-ray diffraction techniques. The structure of 8 consists of a pseudo-octahedral PtRu5 cluster with a second platinum atom bridging a basal edge of the Ru5 square pyramid. A triply bridging PhC2H ligand is bonded to the two platinum atoms and one of the ruthenium atoms. The structure of 9 consists of a nido-dodecahedral Pt2Ru5 cluster with a carbido ligand in the interior that is not bonded to all seven of the metal atoms. It also contains two triply bridging PhC2H ligands. The structure of 10 consists of a central octahedral cluster of five ruthenium atoms and one platinum atom. Two additional platinum atoms are bonded to the platinum atom in this cluster but these atoms are not bonded to any other metal atoms of the PtRu5 cluster. A triply bridging PhC2H ligand is coordinated to the group of three platinum atoms. The structure of 11 consists of an octahedral PtRu5 cluster with two additional platinum atoms capping two PtRu2 triangular faces. There are two PhC2Ph ligands bridging two Ru3 triangular faces of the central octahedron.

Synthesis and characterization of mononuclear copper(II) and dinuclear cadmium(II) complexes with di-(2-picolyl)sulfide

The reaction of CuCl2 · 2H2O and CdCl2 with di-(2-picolyl)sulfide (dps) leads to the formation of mononuclear copper(II) and binuclear cadmium(II) complexes, [Cu(dps)Cl2] · H2O (1) and [(dps)(Cl)CdII(μ-Cl)2CdII(Cl)(dps)] (2). The copper atom in (1) is coordinated to one sulfur and two nitrogen atoms from the dps ligand and two chlorides in a distorted square-pyramidal environment. Complex (2) has two distorted octahedra sharing the basal edge that contain the bridging chloro ligands, each of which resides at a center of inversion. Cyclic voltammetric data show that (1) undergoes two reversible one-electron waves corresponding to CuII/CuIII and CuII/CuI processes. However, cyclic voltammetry of (2) gives two irreversible reduced waves.

The 2M1 dioctahedral mica polytype: A crystal chemical study

AbstractThe structure of dioctahedral true micas such as muscovite and celadonitic muscovite (2M1 polytype, space group C2/c) is mostly affected by variations of the octahedral Al (VIAl) content. Crystals with greater Mg, Fe substitutions (i.e. celadonitic muscovite) reduce the dimensional difference between the larger trans-oriented M1 site and smaller cis-oriented M2 octahedral site. The octahedral anionic position O4 is displaced from the center of the hexagon, defined by 031 and 032 oxygen atoms (i.e. ‘octahedral hexagon’), both on and off the (001) plane. The distance between interlayer cation A and O4 is smaller in more substituted species, thus providing different orientations of the O4−H vector, as a function of VIAl. Octahedral distances (<M2−O3> and <M2−O4> are expressed as a function of cell parameters and VIA1 content, thus allowing an approximate estimate of site dimensions. These approximations are useful when a detailed structural refinement is not available. In celadonitic muscovite, the octahedral hexagon mean edge (<O31−O32>Hex) is not significantly affected by VIA1 content. The VIA1 increase produces both a decrease in cell lateral dimensions and a distorted ‘octahedral hexagon’. The decrease in a and b is consistent with a decrease of <O31−O32>Hex, whereas the distortion of the’ octahedral hexagon’ is consistent with an increase of (<031–032>Hex), because an irregular hexagon produces a longer mean edge than a regular hexagon of equal area.The tetrahedral mean basal edge (VI<O−O>bassal) is reduced as celadonitic substitution progresses. The tetrahedral rotation angle, α was thus found to increase from celadonite to muscovite. However, in muscovite with VIAl content between 1.8 and 2.0 atoms per formula unit (a.p.f.u.), α approaches a saturation value, thus showing a proportional increase of tetrahedral and octahedral sheet lateral dimensions. Furthermore, α variation allows a coarse approximation of the threshold VIAl content, below which celadonitic substitution may not progress.

The new semiconducting polychalcogenide Ba 2SnSe 5 exhibiting [formula omitted] units and distorted SnSe 6 octahedra

The new polyselenide Ba 2SnSe 5 was prepared from the elements under exclusion of air at temperatures between 650 and 750 °C. Ba 2SnSe 5 crystallizes in the orthorhombic space group P2 12 12 1, with the lattice parameters of a = 12.3572 ( 8 ) Å , b = 17.235 ( 1 ) Å , c = 18.134 ( 1 ) Å , V = 3862.1 ( 4 ) Å 3 ( Z = 16 ). Its structure comprises nonlinear Se 3 2 - trimers, isolated SnSe 4 tetrahedra and trimeric Sn 3Se 10 units, the latter consisting of a central (distorted) SnSe 6 octahedron sharing two opposite basal edges with two SnSe 4 tetrahedra. The structural differences to its Sr and Te analogs, Sr 2SnSe 5 and both modifications of Ba 2SnTe 5, are intriguing, and illustrated in detail in this article. Ba 2SnSe 5 is a dark brown semiconductor with a computed band gap of 1.2 eV.

Molecular dynamics simulations of basal and pyramidal system edge dislocations in sapphire

Directionally solidified ceramic eutectics containing alumina as a topologically continuous majority component with, e.g., yttria-stabilized cubic-zirconia or with YAG as minority components have become of considerable interest as members of a new family of potential high temperature structural materials. The attractive creep resistance of such eutectics in fiber-form is based on their remarkably tight [0 0 0 1] texture of the alumina component in which neither the basal plane nor the prism plane can be activated to result in glide that can extend the eutectic by creep in tension. Under such conditions creep in such eutectics must be governed by climb of the (1/3) 1 ¯ 101 edge dislocations out of either the ( 11 2 ¯ 0 ) prism plane or the ( 1 1 ¯ 02 ) pyramidal plane. To develop better understanding of the core structure of these dislocations and their potential role in the creep resistance of the alumina component in eutectics with tight [0 0 0 1] textures, a molecular dynamics (MD) simulation was carried out of the comparative core structures of both the (1/3) 2 1 ¯ 1 ¯ 0 basal edge dislocations and the (1/3) 1 ¯ 101 pyramidal edge dislocations on the ( 1 1 ¯ 02 ) plane in sapphire. The MD simulation revealed that the equilibrium structure of the core of the pyramidal edge dislocations undergo a dissociation into two half strength partial edge dislocations displaced vertically out of the best glide plane of cation holes with weak covalent bonding and possible fair glide resistance into two adjacent pyramidal planes of very strong covalent bonding, and consequent, very high glide resistance. While this explains the immobility in glide of such dislocations on the pyramidal system, no important structural impediment was found for their climb motion out of the pyramidal planes.

Effect of Substrate Orientation on the Growth Rate and Surface Morphology on GaSb Grown by Metal-Organic Vapor Phase Epitaxy

AbstractMOVPE of GaSb grown on (100), (111)A and (111)B GaSb substrates were investigated to study the effect of substrate orientation on the growth rate and surface morphology. Besides growth temperature and V/III ratio, the GaSb growth rate strongly depends on the crystallographic orientation. As the V/III ratio rises, the growth rate on the (111)B oriented substrate decreases, whereas that on the (111)A oriented substrate increases. The surface morphology on different substrates was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). On (111)A substrates, triangular hillocks are the dominant defects, while on (111)B planes, three distinct types of hexagonal hillocks are observed, namely, non-flat top hexagonal structure with spiral growth features (Type I), flat top structure with lateral growth features (Type II), and non-flat top hexagonal structure with multiple islands (Type III). For all types, the basal edges of each hillock are preferentially aligned along <110> directions. A closer look reveals that the top surface of Type II feature consists of many levels of small hexagonal shaped terraces, with each step height in the monolayer range, indicating a step flow growth involved.

Investigation on the growth and structure of Fe-doped near-stoichiometric LiNbO3crystal

The Fe-doped near-stoichiometric LiNbO3 crystal has been grown from the Li-rich melt by Czochralski method. The UV-Vis absorption spectra, IR transmittance spectra and X-ray diffraction were measured and used to study the defect structure of the crystal. Compared with that of congruent Fe:LiNbO3, in near-stoichiometric Fe:LiNbO3, the lattice parameter reduces, the basal absorption edge shifts towards shorter wavelength, and the OH stretching vibration absorption band shifts towards the lower wavenumber side (3466 cm−1) in the Fe-doped near-stoichiometric LiNbO3.

Surface modification studies of edge-oriented molybdenum sulfide nanosheets.

We have synthesized edge-oriented MoS2 nanosheets by the evaporation of a single source precursor based on Mo(IV)-tetrakis(diethylaminodithiocarbomato). The surface chemistry of the MoS2 nanosheets has been studied in order to evaluate the chemical reactivities of the basal planes and edges. By irradiating the MoS2 nanosheet with a scanning infrared laser, micron-scale lithographical structures can be created due to laser-induced oxidation of MoS2 to form nanocrystalline MoO3. Preferential reactivities of the MoS2 basal edges in an electrochemical environment and during vapor phase deposition have been demonstrated. Functionalization of the basal plane with 1-pyrene acetic acid allows the immobilization of DNA and immunoglobins on the MoS2 basal plane.

Place-pitch and excitation patterns in cochlear implant listeners

In cochlear implants (CIs), an electrode’s pitch is largely determined by the excitation pattern produced by stimulation. For CI users, is pitch perception most strongly influenced by the peak, edge or some intermediate location within the excitation pattern? By varying the stimulation mode at four evenly spaced electrode locations, four spectral profiles were hypothesized: single-peaked, apically weighted, basally weighted or multi-peaked (with an intermediate pitch). Forward-masked excitation patterns and pitch judgments were obtained for the four electrode locations, for all experimental stimulation modes, relative to a standard set of BP1 electrodes. Results showed individual differences in CI users’ excitation patterns and pitch judgments produced by the different stimulation modes. Most subjects’ pitch judgments were sensitive to single, sharp peaks in the excitation pattern; however, subjects differed in their sensitivity to broader, multi-peaked patterns. For widely spaced electrode configurations, some subjects consistently judged pitch according to the apical edge of stimulation, some to the basal edge and others to an intermediate location. For some electrode locations, varying the stimulation mode produced significantly different pitches and excitation patterns. Future speech processing strategies may wish to combine stimulation modes to improve the spectral resolution available with a fixed number of implanted electrodes.

Synthesis and characterization of a novel chloro-bridged bis cadmium(II) complex with bis(2-pyridylmethyl)amino-4-butyric acid

The reaction of CdCl 2 with bis(2-pyridylmethyl)amino-4-butyric acid (Hpmab) leads to the formation of binuclear complex [(Hpmab)(Cl)Cd II(μ-Cl) 2Cd II(Cl)(Hpmab)] ( 1). Complex 1 can be regarded as two distorted octahedrons sharing the basal edge that contain the bridging chloro ligands, in each of which resides at a center of inversion. Cyclic voltammetry of 1 gives one oxidation and two reduced processes.

A seamless system for the collection and cultivation of extremophiles from deep-ocean hydrothermal vents

Pele's Pit is a 300-m-deep pit crater whose summit rises to a depth of 1000 m on the Loihi submarine volcano 34 km south of the island of Hawaii. Hydrothermal vents with water temperatures up to 198/spl deg/C have been observed at the basal edge of the pit. We fabricated a seamless system comprising submersible-mounted samplers, a helium-activated sample transfer system, and a series of 1-l Teflon-lined stainless-steel bioreactors that maintain ambient temperature and pressure in hydrothermal vent fluids collected from hydrothermal vents in the pit crater. The bioreactors can sustain pressures to 150 atm. and temperatures over 165/spl deg/C. The system was deployed during October 2001 Pisces V submersible operations on Pele's Pit during which the maximum vent water temperature measured was 90/spl deg/C.

Development of an in vivo model to study testicular morphogenesis.

We have developed an in vivo model to examine testicular cord formation by isolated Sertoli and myoid cells when implanted under the kidney capsule of severe combined immunodeficient (SCID) mice. Neonatal porcine Sertoli (92.5% +/- 3.5%) and myoid (2.2% +/- 0.7%) cellular aggregates were transplanted underneath the kidney capsule of SCID mice. Grafts were removed between 0 and 60 days posttransplantation and examined histologically for the progressive development of structures resembling testicular cords. Aggregates began to reorganize by day 3, and cord structures were present at day 7 posttransplantation. These structures became larger and more defined as the time progressed after implantation. To localize Sertoli and peritubular myoid cells, grafts were immunostained for the Sertoli cell proteins, vimentin, DNA transcription factor GATA-4, and Müllerian inhibiting substance (MIS), as well as for a myoid cell protein, smooth muscle alpha-actin. In the "seminiferous" epithelial layer, the Sertoli cells were arranged with their nuclei along the basal edge adjacent to the peritubular myoid cells that were surrounding the tubules. Moreover, the expression of MIS mimicked that during porcine testicular development, suggesting the Sertoli cells were developing normally. In addition, proliferating cell nuclear antigen (PCNA) was detected in the Sertoli cells at all time points, indicating the proliferation of Sertoli cells in the grafts, which is consistent with Sertoli cell proliferation prior to puberty in the native porcine testis. These results suggest that the specific factors required for cord formation and prepubertal development are inherent in the transplanted cells. Moreover, we have developed a novel in vivo transplantation model to study seminiferous cord formation and prepubertal development.

Substituted boat-shaped Co 6 carbonyl cluster derivatives containing a semi-interstitial P atom and both bridging dithiolate and heterocyclic phosphido ligands

The reaction of Co 2(CO) 8 with Cl PSCH 2CH 2CH 2S gives the Co 6 cluster Co 6(μ 6-P)(μ-SCH 2CH 2CH 2S)(μ- PSCH 2CH 2CH 2S )(CO) 12 ( 5). X-ray structural analysis of 5 revealed that six Co atoms form a boat-shaped array consisting of a basal square of four cobalt atoms with two opposite edges bridged by two apical Co atoms, a semi-interstitial P atom, a propanedithiolate ligand doubly bridging a basal side and a heterocyclic phosphido ligand bridging the opposite basal edge. Reaction of 5 with PPh 3 results in the formation of the mono-substituted products (Co 6(μ 6-P)(μ-SCH 2CH 2CH 2S)(μ- PSCH 2CH 2CH 2S )(μ-CO)(CO) 10(PPh 3) ( 6) and (Co 6(μ 6-P)(μ-SCH 2CH 2CH 2S)(μ- PSCH 2CH 2CH 2S )(μ-CO)(CO) 11(PPh 3) ( 7). Reaction of (Co 6(μ 6-P)(μ-SCH 2CH 2S)(μ- PSCH 2CH 2S )(CO) 12 ( 4) with PPh 3 at higher temperature results in the formation of the di-substituted cluster Co 6(μ 6-P)(μ-SCH 2CH 2S)(μ- PSCH 2CH 2S )(CO) 10·(PPh 3) 2 ( 8). Reactions of 5 with P(OEt) 3 result in the substitution of one or two carbonyl groups to give (Co 6(μ 6-P)(μ-SCH 2CH 2CH 2S)(μ- PSCH 2CH 2CH 2S )(CO) 11P(OEt) 3)} ( 9) and {Co 6(μ 6-P)(μ-SCH 2CH 2CH 2S)(μ- PSCH 2CH 2CH 2S )(CO) 11(P(OEt) 3)} ( 9′) with different spectral data from that of ( 9), and {Co 6(μ 6-P)(μ-SCH 2CH 2CH 2S)(μ- PSCH 2CH 2CH 2S )(μ-CO)(CO) 9(P(OEt) 3) 2} ( 10). X-ray structural analysis of 10 identified the sites of phosphite substitution as the two apical Co atoms. A semi-bridging CO group in 10 is located on a basal side. The IR ν(CO) solution spectrum of 10 does indicate the existence of the semi-bridging CO group in the solution as well.

Direct Synthesis of Heterometallic Europium/Barium Complexes: H2[Eu2Ba6O2(OiPr)16(THF)4] and EuBa2(OC6H4Me-4)7(diglyme)2(DME)

Convenient syntheses of mixed-metal Eu/Ba complexes starting from the elemental metals have been explored. A mixture of europium and barium ingots reacts in boiling 2-propanol to form a product which crystallizes from THF as the heterometallic complex formulated as H2[Eu2Ba6O2(OiPr)16(THF)4] (1). An analogous reaction in the presence of p-cresol (HOC6H4Me-4) forms trimetallic EuBa2(OC6H4Me4)7(diglyme)2(DME) (2), after recrystallization from THF/DME/diglyme (DME = 1,2-dimethoxyethane). Complex 1 exhibits an octametallic geometry comprised of two square pyramids with coplanar bases which share a basal edge and have apices on opposite sides. The six barium atoms occupy the basal positions and the two europium atoms are at the apices. Complex 2 exhibits a triangular arrangement of metal atoms with both terminal and bridging aryloxide ligands coordinated to the europium atom and bridging aryloxide and terminal ether ligands coordinated to the barium atoms.

Skeletal Growth by Condensation of Small Metal Fragments on a Carbido Carbonyl Cluster. Synthesis of the Anions [Rh15C2(CO)24X2]3- (X = Cl, Br, I) and Molecular Structure of the Bromo and Iodo Derivatives

The reaction of [Rh12C2(CO)24]2- (as K+ salt) with RhI derivatives yields an uncharacterized intermediate (1) from which, by reaction with halides, the new carbido-carbonyl cluster anions [Rh15C2(CO)24X2]3- (X = Cl, 2a; Br, 2b; I, 2c) have been obtained. The molecular structures of 2b and 2c as [N(n-Pr)4]+and [NEt4]+ salts, respectively, have been determined by single-crystal X-ray diffractometry. The two anions are isostructural and contain a Rh15C2 cluster that can be described as a C2v centered and tetracapped pentagonal prism. The carbide atoms occupy octahedral interstices, and the halide ligands span basal edges of the prism. The CO ligands have been found partially ordered in the dibromo derivative and totally ordered in the diiodo one, adopting an unprecedented and peculiar asymmetric stereogeometry. The room-temperature solution 13C NMR spectrum indicates that in compound 2c a fraction of the carbonyl ligands is fluxional, probably those found disordered in the solid state structure of 2b.

Uptake, Distribution, and Metabolism of 1-Naphthaleneacetic Acid and Indole-3-Acetic Acid During Callus Initiation From Actinidia deliciosa Tissues.

1-Naphthaleneacetic acid (NAA) and 6-benzyladenine (BA) were required for in vitro callus formation at the basal edge of kiwifruit (Actinidia deliciosa [A. Chev] Liang and Ferguson, cv. Hayward) petioles. The uptake, metabolism, and concentration of NAA and indole-3-acetic acid (IAA) content were examined in the explants during the callus initiation period. After 1, 6, 12, 24, 48, and 96 h of culture in the presence of [H(3)]NAA, petioles were divided into apical, middle, and basal portions and analyzed. Except for a high IAA level measured at 12 h, IAA content decreased in tissues during a culture period of 96 h. NAA uptake was higher in petiolar edges than in the middle portion, and NAA was rapidly conjugated with sugars and aspartic acid inside the tissues. The amide conjugation was triggered in apical and basal portions from 12 h and in the middle part from 48 h, with alpha-naphthylacetylaspartic acid being the major metabolite. Free-NAA concentration in cultured petioles achieved an equilibrium with the exogenously applied NAA (0.27 µm) from 12 h, and it remained constant thereafter. The relationships between the role attributed to NAA and BA in the initiation and the maintenance of disorganized growth of callus in kiwifruit cultures are discussed.

Electrophilic Additions of Mercury and Gold Species to the Anion Carbide Cluster [Fe5C(CO)14]2-. X-ray Crystal Structures of (NEt4)[Fe5C(CO)14{μ-HgW(CO)3Cp}] and (NEt4)2[μ4-Hg{Fe5C(CO)14}2

The reaction of the carbide carbon anion [Fe5C(CO)14]2- with ClHgM in tetrahydrofuran gives the new heptametallic clusters (NEt4)[Fe5C(CO)14{μ-HgM}] (M = Mo(CO)3Cp (1a), W(CO)3Cp (1b), Mn(CO)5 (1c), Co(CO)4 (1d), Fe(CO)2Cp (1e)). The spiro species (NEt4)2[μ4-Hg{Fe5C(CO)14}2] (2) has been isolated by reaction of the pentairon carbide carbon dianion with Hg(NO3)2. The structures of 1b and 2 have been determined by X-ray diffraction methods. The anion of 1b has an Fe5 square-pyramidal metal skeleton in which a basal edge is bridged by the HgW(CO)3Cp moiety. For the cluster anion 2, the metal core consists of a four-coordinate mercury atom bridging the bond edges of two square-based-pyramidal pentairon units. The electrochemical behavior of these compounds has been investigated by cyclic voltammetry and coulometry. The 57Fe Mossbauer spectroscopy of complexes 1b,e reveals the existence of three and four types of iron sites, respectively. This study has been extended by reacting the new species (NEt4)[Fe5C(CO)...

A New Polymorph of VO2Prepared by Soft Chemical Methods

A novel polymorph of VO2, designated VO2(C), has been prepared by dehydration of the new layered vanadium oxide hydrate, VO2·1/2 H2O. The hydrate is prepared in high yield as a single phase from the hydrothermal reaction of the hydrolyzate of VCl4and NaOH in a molar ratio of 1:4.5 for 96 hours at 200°C. The hydrate crystallizes in the tetragonal space groupI4/mmm, witha=3.7211(6) Å,c=15.421(1) Å,Z=4, andR=0.045 as determined by X-ray single crystal diffraction. The structure consists of layers of VO5square pyramids, each of which shares its four basal edges with four neighboring VO5square pyramids. Water molecules that reside between the layers can be removed reversibly to give the new layered oxide VO2(C).