Topic
Single crystal
About: Single crystal is a research topic. Over the lifetime, 59617 publications have been published within this topic receiving 870828 citations.
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TL;DR: The phase behavior of mixed A-site cation methylammonium (MA)/formamidinium (FA) lead iodide hybrid perovskites FAxMA1−xPbI3 has been investigated using powder and variable temperature single crystal X-ray diffraction, with A site composition determined by 1H solution NMR.
Abstract: The phase behaviour of mixed A-site cation methylammonium (MA)/formamidinium (FA) lead iodide hybrid perovskites FAxMA1−xPbI3 has been investigated using powder and variable temperature single crystal X-ray diffraction, with A site composition determined by 1H solution NMR. At room temperature, the crystal class is cubic across the composition range 0.2 ≤ x ≤ 1 but a tetragonal phase is observed for x = 0 (MAPbI3) and x = 0.1. Cooling cubic FAxMA1−xPbI3, 0.2 ≤ x ≤ 1, phases below room temperature results in a phase change to a larger unit cell with tilted [PbI6] octahedra and the temperature at which this occurs, TC→T, decreases sharply until x = 0.2 (TC→T = 257 K) before steadily increasing to TC→T = 283 K for FA0.9MA0.1PbI3. The lattice parameters and optical band gap of cubic FAxMA1−xPbI3, 0.2 ≤ x ≤ 1 at 298 K have been shown to vary in accordance with Vegard's law, though a larger band gap is observed for the tetragonal phases, 0.0 ≤ x ≤ 0.1.
130 citations
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TL;DR: A selective etching phenomenon on {001} faceted anatase TiO(2) single crystal surfaces by HF and associated etching mechanism are reported and density functional theory calculations reveal that HF stabilizes the grown facets at low concentrations, but selectively destroys the growing facets at high concentrations.
130 citations
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130 citations
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TL;DR: First-principles DFT computation results show that Zn vacancies can induce intrinsic ferromagnetism in these undoped ZnS NWs and indicate that the magnetic moment of the ultrathin Zn S NWs can be increased by increasing the Zn vacancy concentration without significant energy cost.
Abstract: Highly uniform single crystal ultrathin ZnS nanowires (NWs) with 2 nm diameter and up to 10 μm length were fabricated using a catalyst-free colloidal chemistry strategy. The nanowires crystallized in hexagonal phase structure with preferential growth along the direction of the (001) basal plane. The strong polarity of the (001) plane composed of Zn cations or S anions drives the oriented attachment of ZnS nanocrystals (NCs) along this direction via electrostatic (or dipole) interaction. The ultrathin ZnS nanowires show intrinsic ferromagnetism at room temperature and other unusual properties related to its unique nature, such as large anisotropic lattice expansion, large blue-shift of UV–vis absorption band of the excition, and photoluminescence spectrum of the exciton band edge. First-principles DFT computation results show that Zn vacancies can induce intrinsic ferromagnetism in these undoped ZnS NWs. The main source of the magnetic moment arises from the unpaired 3p electrons at S sites surrounding the...
130 citations
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TL;DR: In this article, the authors measured the strain dependence of four high-frequency vibrational modes in a single crystal of toluene sulfonate diacetylene polymer and obtained an ultimate tensile strength of 2.0 × 109 N m−2.
Abstract: Resonance Raman spectroscopy has been used to measure the strain dependence of four high-frequency vibrational modes in a single crystal of toluene sulfonate diacetylene polymer. The 0.62-μm thick crystal was stretched elastically to 4% strain before fracture occurred. This was equivalent to an ultimate tensile strength of 2.0 × 109 N m−2. The strain dependence of the vibrational modes has been interpreted using a simple point mass and anharmonic spring constant model. A Fermi resonance was observed for two vibrational modes which are degenerate at 2.1% strain and a 1464 cm−1 frequency.
129 citations