Academic literature on the topic 'TRIGONAL LATTICES'

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Journal articles on the topic "TRIGONAL LATTICES"

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Kontrym-Sznajd, G., and M. Samsel-Czekała. "Special directions in momentum space. II. Hexagonal, tetragonal and trigonal symmetries." Journal of Applied Crystallography 45, no. 6 (November 15, 2012): 1254–60. http://dx.doi.org/10.1107/s0021889812041283.

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This paper is a continuation of a previous one,Special directions in momentum space. I. Cubic symmetries[Kontrym-Sznajd & Samsel-Czekała (2011).J. Appl. Cryst.44, 1246–1254], where new sets of special directions (SDs), having the full symmetry of the Brillouin zone, were proposed for cubic lattices. In the present paper, such directions are derived for structures with unique six-, four- and threefold axes,i.e.hexagonal, tetragonal and trigonal lattices, for both two- and three-dimensional space. The SDs presented here allow for construction, in the whole space, of anisotropic quantities from the knowledge of such quantities along a limited number of SDs. The task at hand is to determine as many anisotropic components as the number of available sampling directions. Also discussed is a way of dealing with data when the number of anisotropic components is restricted by a non-optimal set of SDs.
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Essén, Hanno, and Arne Nordmark. "Some results on the electrostatic energy of ionic crystals." Canadian Journal of Chemistry 74, no. 6 (June 1, 1996): 885–91. http://dx.doi.org/10.1139/v96-097.

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We define a class of ionic cyrstals, the alternating Bravais lattice ionic crystals, which has the NaCl and CsCl structures as members. We calculate the electrostatic energy of finite pieces and study the convergence to the macroscopic Madelung limit. For the one-parameter family of trigonal lattices we calculate the dependence of the electrostatic energy on the parameter. The NaCl and CsCl structures correspond to minima, the CsCl minimum being deeper. This is due to long-range effects; for small clusters the NaCl structure is favored. We also study the Madelung constant of simple cubic lattices as a function of spatial dimension, and discuss the results. We finally calculate the electrostatic repulsion of two constant unit charge distributions in the unit cube. This quantity, a six-dimensional integral, can be integrated analytically five times, leaving a simple one-dimensional integral to be done numerically. Key words: ionic crystal, Madelung constant, ionic cluster, electrostatic energy.
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Takeshita, T., C. Tomé, H. R. Wenk, and U. F. Kocks. "Single-crystal yield surface for trigonal lattices: Application to texture transitions in calcite polycrystals." Journal of Geophysical Research 92, B12 (1987): 12917. http://dx.doi.org/10.1029/jb092ib12p12917.

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Beattie, JK, SP Best, FH Moore, BW Skelton, and AH White. "Water Molecule Dispositions in the Cesium Sulfate α- and β-Alums: Single-Crystal Neutron Diffraction Studies of CsM(SO4)2.12H2O (M=V, Rh)." Australian Journal of Chemistry 46, no. 9 (1993): 1337. http://dx.doi.org/10.1071/ch9931337.

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Room-temperature single-crystal neutron diffraction studies are recorded for two alums, Cs( Rh /V)(SO4)2.12H2O [cubic, Pa3, a 12.357(5) ( Rh ), 12.434(1)Ǻ (V)], residuals 0.037 and 0.068 for 328 and 164 'observed' reflections, with the intention of defining water molecule hydrogen atom orientations. Whereas the two tervalent hexaaqua cations are similar in size [ rM -O = 2.010(6)Ǻ (M = V) and 2.006(2)Ǻ (M = Rh )] the vanadium salt adopts the β alum modification while rhodium gives an α alum. Significantly, the water coordination geometry is different in the two cases with the tilt angle between the plane of the water molecule and the M-O bond vector being 1° (M = V) and 35° (M = Rh ). The tilt angle for water coordinated to rhodium in CsRh (SeO4)2.12H2O is inferred from the unit cell dimensions to be similar to that of the corresponding sulfate salt and not that which generally pertains for caesium selenate alums. Significant differences in the H-O-H bond angle are found for trigonal planar and trigonal pyramidal water coordination, suggesting that differences in the metal(III)-water interaction are a determinant of the geometry of the coordinated water molecule in the caesium sulfate/ selenate alum lattices.
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Kayalvizhi, M., and L. John Berchmans. "Combustion Synthesis of Lanthanum Substituted LiNiO2Using Hexamine as a Fuel." E-Journal of Chemistry 7, s1 (2010): S137—S142. http://dx.doi.org/10.1155/2010/467818.

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Lithium nickelate and its lanthanum substituted compound have been successfully prepared by combustion synthesis process using LiNO3, Ni(NO3)2.6H2O and La(NO3)3.6H2O. Hexamine is used as fuel. The physicochemical properties of the powders were investigated by thermal analysis (TGA/DTA). The crystalline powders were characterized for their phase identification using x-ray diffraction analysis (XRD). FT-IR spectroscopy was used to study the local structure of the oxide environment. The morphological features of the powders were characterized by scanning electron microscopy (SEM). DTA analysis reveals the evolution of an exothermic peak at 465oC indicating the rapid decomposition of the hexamine and dissociation of nitrate salts, forming the final compound lithium nickealte. The XRD pattern reveals the rhombohedral structure of LiNiO2with trigonal symmetry comprising of two interpenetrating close packed FCC sub-lattices. The lattice constant values ̒a̓ and ̒c̓ are in good agreement with the reported data. In the FT-IR spectra, vibrational bands are identified in the range of 400-800 cm-1representing the NiO2layer. LiNiO2exhibits a very fine crystalline structure with an irregular morphology. The La substituted LiNiO2powder has shown a smooth-edged polyhedral structure with an average particle size of 5-10 μm.
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Janner, A. "Symmetry-adapted digital modeling I. Axial symmetric proteins." Acta Crystallographica Section A Foundations and Advances 72, no. 3 (March 30, 2016): 298–311. http://dx.doi.org/10.1107/s2053273316002746.

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Considered are axial symmetric proteins exemplified by the octameric mitochondrial creatine kinase, the Pyr RNA-binding attenuation protein, the D-aminopeptidase and the cyclophilin A–cyclosporin complex, with tetragonal (422), trigonal (32), pentagonal (52) and pentagonal (52) point-group symmetry, respectively. One starts from the protein enclosing form, which is characterized by vertices at points of a lattice (the form lattice) whose dimension depends on the point group. This allows the indexing of Cα's at extreme radial positions. The indexing is extended to additional residues on the basis of a finer lattice, the digital modeling lattice Λ, which includes the form lattice as a sublattice. This leads to a coarse-grained description of the protein. In the crystallographic point-group case, the planar indices are obtained from a projection of atomic positions along the rotation axis, taken as thezaxis. The planar indices of a Cαare then those of the nearest projected lattice point. In the non-crystallographic case, low indices are an additional requirement. The coarse-grained bead follows from the condition imposed on the residues selected to have azcoordinate within a band of value δ above and below the height of lattice points. The choice of δ permits a variation of the coarse-grained bead model. For example, the value δ = 0.5 leads to a fine-grained indexing of the full set of residues, whereas with δ = 0.25 one gets a coarse-grained model which includes only about half of these residues. Within this procedure, the indexing of the Cαonly depends on the choice of the digital modeling lattice and not on the value of δ. The characteristics which distinguish the present approach from other coarse-grained models of proteins on lattices are summarized at the end.
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Yang, X. L., L. Z. Cai, Y. R. Wang, and Q. Liu. "Interference of four umbrellalike beams by a diffractive beam splitter for fabrication of two-dimensional square and trigonal lattices." Optics Letters 28, no. 6 (March 15, 2003): 453. http://dx.doi.org/10.1364/ol.28.000453.

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Yang, X. L., L. Z. Cai, Y. R. Wang, and Q. Liu. "Interference technique by three equal-intensity umbrellalike beams with a diffractive beam splitter for fabrication of two-dimensional trigonal and square lattices." Optics Communications 218, no. 4-6 (April 2003): 325–32. http://dx.doi.org/10.1016/s0030-4018(03)01231-8.

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Grabner and Modec. "Zn(II) Curcuminate Complexes with 2,2’-bipyridine and Carboxylates." Molecules 24, no. 14 (July 11, 2019): 2540. http://dx.doi.org/10.3390/molecules24142540.

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Two novel zinc(II) compounds with curcuminate (abbreviated as cur–), [Zn(CH3COO)(cur)(bpy)](1)·CH3OH·2H2O (bpy = 2,2’-bipyridine) and [Zn(PhCOO)(cur)(bpy)] (2)·CH3OH, have been synthesized and characterized. Their composition has been determined by single-crystal X-ray structure analysis. Complexes 1 and 2 are similar: in both a five-fold coordination environment of zinc(II) consists of a monodentate carboxylate, a chelating bidentate 2,2’-bipyridine, and curcuminate, which is bound via a deprotonated 1,3-dione moiety. In 1, 2,2’-bipyridine nitrogen atoms and curcuminate oxygen atoms form the base of a square pyramid, whereas the acetate oxygen occupies its apex. The O3N2 donor set in 2 defines a polyhedron which more closely resembles a trigonal bipyramid. The packing in the crystal lattices of both compounds is governed by hydrogen-bonds. Complexes 1 and 2 display higher stability than curcumin in buffered media at pH = 7.0, however, the degradation of coordinated cur– is comparable to that of yellow pigment curcumin (curH) when the pH is raised to 7.2. Both complexes 1 and 2 in DMSO exhibit fluorescence with Stokes shifts of 5367 and 4634 cm−1, respectively.
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Hirakawa, Satoru, and Hisashi Honda. "1H and 13C NMR and Electrical Conductivity Studies on New Ionic Plastic Crystals of Tetraalkylammonium Tetraethylborate." Zeitschrift für Naturforschung A 70, no. 7 (July 1, 2015): 521–28. http://dx.doi.org/10.1515/zna-2015-0105.

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AbstractEight plastic crystals of the types NEtxMe(4 − x)BEt4 and NEtyPr(4 − y)BEt4 (x=0–4, y=1–3) were found in a new region of ionic plastic crystals. In this area, globular cations and anions are assembled by weak interactions. Based on the results of solid-state 1H and 13C nuclear magnetic resonance (NMR) measurements, it was revealed that the ions performed isotropic reorientations in the NEtxMe(4–x)BEt4 crystals (x=0–4). Additionally, X-ray diffraction (XRD) of these compounds was able to identify the CsCl-type cubic structure. In contrast, the XRD reflections of NEtyPr(4−y)BEt4 (y=1–3) could be successfully fitted by distorted cubic lattices (trigonal symmetry). The NMR line shapes observed in these compounds were explained by overall molecular motions with large amplitudes (pseudo-isotropic reorientations). Differential scanning calorimetry (DSC) spectra of NEtyPr(4 − y)BEt4 (y=1–3) showed a low entropy change (ΔSmp) of 6–8 J K−1 mol−1 at the melting point. Ionic diffusion was identified by electrical conductivity measurements of NEtxMe(4 − x)BEt4 and NEtyPr(4–y)BEt4 (x=0–4, y=1–3). In the case of NPr4BEt4 crystals, ionic diffusion was also detected, although complex powder patterns and large ΔSmp values were observed by XRD and DSC measurements, respectively.
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Dissertations / Theses on the topic "TRIGONAL LATTICES"

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Gardner, N. J. G. "Structure and dynamics of superionic conductors at high temperatures and high pressures." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325955.

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BONTURIM, EVERTON. "Controle de propriedades multiferroicas em filmes finos óxidos dopados com íons terras raras para aplicação como dispositivos lógicos e de memória." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28033.

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Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-22T14:03:18Z No. of bitstreams: 0
Made available in DSpace on 2017-11-22T14:03:18Z (GMT). No. of bitstreams: 0
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Nas últimas décadas, o consumo de dispositivos eletrônicos e a alta demanda por armazenamento de dados tem mostrado grandes oportunidades para a criação de novas tecnologias que garantam as necessidades mundiais na área de computação e desenvolvimento. Alguns materiais multiferroicos tem sido amplamente estudados e o BiFeO3, considerado o único material multiferroico em temperatura ambiente, ganhou destaque como candidato para produção de dispositivos lógicos e de memória. O uso de técnicas de crescimento como a deposição por laser pulsado permitiu a produção de filmes finos de BiFeO3 com elevado controle de qualidade. Heteroestruturas de filmes multiferroicos de BiFeO3 e LaBiFeO3 foram crescidas com diferentes espessuras sobre substratos de SrTiO3(100), DyScO3(110) e SrTiO3/Si(100) para avaliação e teste de suas propriedades elétricas e magnéticas. Filmes ferromagnéticos de Co0,9Fe0,1 foram depositados por sputtering sobre os filmes multiferroicos para avaliação da interação interfacial entre ordenamentos magnéticos. Técnicas como fotolitografia foram utilizadas para padronização de microdispositivos gravados sobre as amostras. Tanto os filmes finos de BiFeO3 como os de LaBiFeO3 foram crescidos epitaxialmente sobre os substratos já cobertos com uma camada buffer de SrRuO3 usado como contato elétrico inferior. A estrutura cristalina romboédrica das ferritas de bismuto foi confirmada pelos dados de difração de raios X, bem como a manutenção de tensão estrutural causada pela rede cristalina do substrato para amostras de 20 nm. Os valores de coeficiente do tensor piezelétrico d33 foram da ordem de 0,15 V (∼ 60 kV.cm-2) para amostras com 20 nm de espessura enquanto que os valores de voltagem coerciva para as análises de histerese elétrica foram da ordem de 0,5 V para as mesmas amostras. A relação de coercividade elétrica com a espessura corresponde ao perfil encontrado na literatura pela relação E≈d-2/3. As amostras de CoFe/BFO e CoFe/LBFO depositadas em diferentes substratos apresentam acoplamento interfacial entre ordenamento ferromagnético e antiferromagnético com momento ferromagnético de rede.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
CAPES:99999.009511/2014-08
CNPq:146622/2013-2
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Marques, Leonel Vitorino Joaquim. "Transformations de phases du C60 sous pression." Université Joseph Fourier (Grenoble ; 1971-2015), 1996. http://www.theses.fr/1996GRE10188.

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Ce mémoire est consacré à l'étude du c60 sous pression. Le diagramme de phases pour le c60 a été établi pour des pressions inférieures à 80kbar. L'application de très hautes pressions (200kbar) à température ambiante transforme le c60 en carbone sp3 et en diamant. A plus basse pression et à haute température, le c60 est converti en carbone sp2 amorphe de type graphitique. Pour des pressions et des températures intermédiaires, trois nouvelles phases polymérisées du c60 ont été obtenues, la structure en cage y est conservée. La phase rhomboedrique et la phase quadratique sont des phases bi-dimensionnelles, la phase orthorhombique est une phase 1d. Dans toutes ces structures, les orientations moléculaires permettent la formation de liaisons intermoléculaires de type cycloaddition 2,2. La nature polymère de ces phases et le type de liaisons ont été obtenues par diffraction x, par calculs théoriques, puis confirmés par rmn solide et spectroscopie ir et raman. Nous suggérons aussi l'existence de polymères 3d à plus forte pression et températures. Leurs structures devraient correspondre à la formation de liaisons interplanaires entre les plans polymérisés
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Book chapters on the topic "TRIGONAL LATTICES"

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Shamsuzzoha, M. "Simple Cubic to Face-Centered-Cubic, as Well as Trigonal Phase Transformations, Due to Inclusion of the Boron in the Lattices of Ni3Al Phase Found at the Grain Boundary Precipitate of Boron-Doped Ni3Al Alloy." In TMS2013 Supplemental Proceedings, 821–28. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118663547.ch102.

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Glazer, A. M. "2. Symmetry." In Crystallography: A Very Short Introduction, 24–38. Oxford University Press, 2016. http://dx.doi.org/10.1093/actrade/9780198717591.003.0002.

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In order to explain what crystals are and how their structures are described, we need to understand the role of symmetry, for this lies at the heart of crystallography. ‘Symmetry’ explains the different types of symmetry: rotational, mirror or reflection, point, chiral, and translation. There are thirty-two point groups and seven crystal systems, according to which symmetries are present. These are triclinic, monoclinic, orthorhombic, tetragonal, trigonal, hexagonal, and cubic. Miller indices, lattices, crystal structure, and space groups are described in more detail. Any normal crystal belongs to one of the 230 space group types. Crystallographers generally use the International Notation system to denote these space groups.
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