The YbTe-SnTe-Bi 2 Te 3 system

International audienc

Intercalation of p-Aminopyridine and p-Ethylenediamine Molecules into Orthorhombic In1.2Ga0.8S3 Single Crystals

International audienceA single crystalline layered semiconductor In1.2Ga0.8S3 phase was grown, and by intercalating p-aminopyridine (NH2-C5H4N or p-AP) molecules into this crystal, a new intercalation compound, In1.2Ga0.8S3·0.5(NH2-C5H4N), was synthesized. Further, by substituting p-AP molecules with p-ethylenediamine (NH2-CH2-CH2-NH2 or p-EDA) in this intercalation compound, another new intercalated compound—In1.2Ga0.8S3·0.5(NH2-CH2-CH2-NH2) was synthesized. It was found that the single crystallinity of the initial In1.2Ga0.8S3 samples was retained after their intercalation despite a strong deterioration in quality. The thermal peculiarities of both the intercalation and deintercalation of the title crystal were determined. Furthermore, the unit cell parameters of the intercalation compounds were determined from X-ray diffraction data (XRD). It was found that increasing the c parameter corresponded to the dimension of the intercalated molecule. In addition to the intercalation phases’ experimental characterization, the lattice dynamical properties and the electronic and bonding features of the stoichiometric GaInS3 were calculated using the Density Functional Theory within the Generalized Gradient Approximations (DFT-GGA). Nine Raman-active modes were observed and identified for this compound. The electronic gap was found to be an indirect one and the topological analysis of the electron density revealed that the interlayer bonding is rather weak, thus enabling the intercalation of organic molecules

Lattice dynamics of Bi2Те3 and vibrational modes in Raman scattering of topological insulators MnBi2Te4·n(Bi2Te3)

This work is devoted to the experimental study and symmetry analysis of the Raman-active vibration modes in MnBi2Te4 center dot n(Bi2Te3) van der Waals topological insulators, where n is the number of Te-Bi-Te-Bi-Te quintuple layers between two neighboring Te-Bi-Te-Mn-Te-Bi-Te septuple layers. Confocal Raman spectroscopy is applied to study Raman spectra of crystal structures with n = 0,1, 2, 3, 4, 5, 6, and infinity. The experimental frequencies of vibration modes of the same symmetry in the structures with different n are compared. The lattice dynamics of free-standing one, three, and four quintuple layers, as well as of bulk Bi2Te3 (n = infinity) and MnBi2Te4 (n = 0), is considered theoretically. Vibrational modes of the last two systems have the same symmetry, but different displacement fields. These fields in the case of a Raman-active mode do not contain displacements of manganese atoms for any finite n. It is shown that two vibrational modes in the low-frequency region of the spectrum (35-70 cm(-1)) of structures with n = 1, 2, 3, 4, 5, and 6 practically correspond to the lattice dynamics of n free quintuple Bi2Te3 layers. For this reason, the remaining two vibration modes, which are observed in the high-frequency region of the spectrum (100-140 cm(-1)) and are experimentally indistinguishable in the sense of belonging to quintuple or septuple layer or to both layers simultaneously, should also be assigned to vibrations in quintuple layers under immobile atoms of septuple layers

Novel ternary layered manganese bismuth tellurides of the MnTe-Bi2Te3 system: Synthesis and crystal structure

It is shown that MnTe-Bi2Te3 system is quasi-binary and in fact hosts three intermediate phases. Along with already known MnBi2Te4 phase, another two, MnBi4Te7 and MnBi6Te10 have been found to exist. All the phases melt incongruently in a very narrow temperature range of 577–590 °C via peritectic reactions. Directional crystal growth results in hetero-phase ingots due to the narrow compositional range and narrow primary crystallization fields. The crystal structure of each phase is a derivation of the prototype tetradymit-type layered structure and the phases constitute a new homologous series with the chemical formula (MnTe)·n(Bi2Te3). X-ray diffraction patterns and Raman spectroscopy of the sorted-out single phase samples show that different phases have different number of the seven (7)- and five (5)-layer blocks and their different stacking manner in the unit cell. In particular, MnBi2Te4 exhibits the -7-7-7-, MnBi4Te7 -5-7-5-7-, and MnBi6Te10 -5-5-7-5-5-7- sequence of the blocks. Thus, these structures are the first derivatives of Bi2Te3 structure to contain a transition metal cation Mn2+

CaracterizaÃÃo metamÃrfica das rochas granulÃticas de Chorozinho-CE

FundaÃÃo de Amparo à Pesquisa do Estado do CearÃConselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoA evoluÃÃo metamÃrfica em terrenos granulÃticos tem sido alvo de intensa pesquisa nas Ãltimas dÃcadas visto que tais terrenos, em sua grande maioria, representam segmentos da crosta continental inferior e mÃdia. Assim, a regiÃo de Chorozinho (Nordeste do CearÃ), exibe uma sequÃncia de rochas granulÃticas, a qual, nÃo dispÃe de estudos envolvendo a determinaÃÃo de idades do metamorfismo da regiÃo, impedidno assim um melhor entendimento desta regiÃo tÃo importante para o contexto geolÃgico do estado do CearÃ. O objetivo do trabalho à encontrar a idade do protÃlito do enderbito, alÃm de determinar condiÃÃes de pressÃo e temperatura dos litotipos representativos das principais unidades aflorantes. A metodologia empregada no desenvolvimento deste trabalho obedeceu quatro etapas diferenciadas, levantamento bibliogrÃfico, etapa de campo, etapa laboratorial, onde as amostras passaram por estudo petrogrÃfico, geocronolÃgico (SHRIMP) e de quÃmica mineral por microssonda eletrÃnica e a etapa de gabinete. A regiÃo de Chorozinho possui trÃs litotipos: gnaisse enderbitico, silimanita-granada-gnaisse (diatexito) e biotita-gnaisse. Destas o primeiro à uma rocha ortoderivada, e apresenta os seguintes minerais identificados em lÃmina: PlagioclÃsio, K-feldspato, Quartzo, Clino e Orto piroxÃnio, Hornblenda, Biotita,  Granada,  Titanita,  ZircÃo,  apatita,  opacos e possuem textura granoblÃstica, enquanto os dois Ãltimos sÃo considerados paraderivados. Sillimanita granada â gnaisse (diatexito) apresentando K-feldspato, Quartzo, PlagioclÃsio, Sillimanita, Biotita,  Opacos  Granada,  apatita,  ZircÃo, e o biotita gnaisse com PlagioclÃsio, K-feldspato, Quartzo, Biotita,  ZircÃo  apatita,  opacos, este podendo ou nÃo ter granada, ambos possuem textura granolepidoblÃstica. A quÃmica mineral mostra que a composiÃÃo da granada à predominantemente almandina, ortopiroxÃnio sÃo enstatita e os clinopiroxÃnios augita e diopsÃdio, os plagioclÃsios demonstraram uma composiÃÃo oligoclÃsio-andesina (caracterÃstica de alto grau metamÃrfico) e os feldspatos alcalino possuem composiÃÃo sanidina. As biotitas revelaram uma tendÃncia a flogopita e eastonita ricas em FeO e TiO2. Com relaÃÃo ao metamorfismo da regiÃo, os softwares, TWEEQU e THERMOCALC, revelaram temperatura, em torno de 700 ÂC e 790 ÂC, e pressÃo entre 4 e 11,6 kbar, para o gnaisse enderbitico. Por fim, Os dados isotÃpicos de U-Pb, em zircÃes, objetivando a idade do protÃlito, forneceram dados esperados devido à proximidade com a idade jà existentes, em torno de 2.1 e 2.0 Ga.The metamorphic evolution of granulite terrains are an intense research mark in the last few decades since, mostly, represent inferior and middle continental crust segments. Thereby, Chorozinhoâs region (CearÃâs northeast) exhibits an granulite rock sequence which doesnât have age determination and regional metamorphism studies, preventing a better understanding of an important region for the Cearà state geological contex. The main objective of this work is to find the protolith age and also determine pressure and temperature conditions for the major outcropping geological units representative lithotypes. The methodology applied in this work followed four differentiated stages, being bibliographical survey, field campaign, laboratorial stage, where the samples went through petrographic, geochronological (SHRIMP) and mineral chemistry (ICP-MS) analysis, and office stage. Chorozinhoâs region possess three lithotypes: enderbitc gneiss, sillimanite-garnet-gneiss (diatexite) and biotite-gneiss. The first is an orthoderived rock and presents these identified minerals in thin section: plagioclase, K-feldspar, quartz, clino and orthopyroxene, hornblend, biotite  garnet  sphene  zircon  apatite  opaque, in granoblastic texture, while the other two are paraderived. Sillimanite-garnet-gneiss (diatextite) have K-feldspar, quartz, plagioclase, sillimanite, biotite  opaque  garnet  apatite  zircon, as the biotite-gneiss have plagioclase, K-feldspar, quartz, biotite  zircon  apatite  opaque, may have or not garnet, and both retain granolepidoblastic texture. The mineral chemistry shows that the garnet composition is mainly almandine, orthopyroxene is enstatite, clinopyroxene are augite and diopside, plagioclase proved to have an oligoclase-andesine composition (high metamorphic grade feature) and alkaline feldspar with sanidine composition. Biotite shown a flogopite/eastonite, rich FeO and TiO2, tendency. Relative to the region metamorphic conditions, the softwares, TWEEQU and THERMOCALC, revealed temperature between 700ÂC-790ÂC and pressure among 4-11,6 kbar, for the enderbitc gneiss. And so, U-Pb isotopic data, in zircon, aiming to define the protolith age, provided the expected information because the proximity with others ages, around 2,1-2,0 Ga