Search results for "crystal growth"

Crystal growth and structural remarks on malonate-based lanthanide coordination polymers

2016

The synthesis, structural characterization and thermal study of new coordination polymers (CPs) of formula [Ln2(mal)3(H2O)5]·2H2O [Ln = Ho (1·2H2O), Tb (1a), Dy (1b), Er (1c) and Yb (1d); mal = malonate], [Ln2(mal)3(H2O)6] [Ln = Sm (2) and Ce (2a)], [Ce2(mal)3(H2O)6]·2H2O (3·2H2O) and [Ce2(mal)3(H2O)3]·2H2O (4·2H2O) are presented. Complexes 1–4 have been also characterized by single crystal X-ray diffraction. The structure of 2 was previously reported (Elsegood, M. R. J., Husain, S., Private Communication, 2014) and it is very close to that of 3. In the light of these results and those previously reported in the literature for malonate-containing lanthanide(III) complexes, a detailed overvi…

The Ultimate Fate of Supercooled Liquids

2010

In recent years it has become widely accepted that a dynamical length scale {\xi}_{\alpha} plays an important role in supercooled liquids near the glass transition. We examine the implications of the interplay between the growing {\xi}_{\alpha} and the size of the crystal nucleus, {\xi}_M, which shrinks on cooling. We argue that at low temperatures where {\xi}_{\alpha} > {\xi}_M a new crystallization mechanism emerges enabling rapid development of a large scale web of sparsely connected crystallinity. Though we predict this web percolates the system at too low a temperature to be easily seen in the laboratory, there are noticeable residual effects near the glass transition that can account …

Protein-induced, previously unidentified twin form of calcite.

2007

Using single-crystal x-ray diffraction, we found a formerly unknown twin form in calcite crystals grown from solution to which a mollusc shell-derived 17-kDa protein, Caspartin, was added. This intracrystalline protein was extracted from the calcitic prisms of the Pinna nobilis shells. The observed twin form is characterized by the twinning plane of the (108)-type, which is in addition to the known four twin laws of calcite identified during 150 years of investigations. The established twin forms in calcite have twinning planes of the (001)-, (012)-, (104)-, and (018)-types. Our discovery provides additional evidence on the crucial role of biological macromolecules in biomineralization.

2019

A probabilistic discrete model for 2D protein crystal growth is presented. This model takesinto account the available space and can describe growing processes of a different nature due to theversatility of its parameters, which gives the model great flexibility. The accuracy of the simulation istested against a real recrystallization experiment, carried out with the bacterial protein SbpA fromLysinibacillus sphaericus CCM2177, showing high agreement between the proposed model and theactual images of the crystal growth. Finally, it is also discussed how the regularity of the interface(i.e., the curve that separates the crystal from the substrate) affects the evolution of the simulation.

On the structural aspects of solid solutions of enantiomers: an intriguing case study of enantiomer recognition in the solid state

2018

Structural aspects of solid solutions of enantiomers have been considered and the corresponding definitions of type 1 and type 2 solid solutions have been revised based on the available structures reported in the literature. Examples of both types are presented indicating that (e.g., type 1 solid solutions) there is a straightforward relationship between the particular structural aspects and the enantiomer miscibility limits in the solid state. Furthermore, enantiomer recognition in a type 2 solid solution formed by the enantiomers of a pharmaceutically active ingredient, pimobendan, has been studied in more detail. It was found that upon rapid crystallization from a solution a structure po…

Fracture flow due to hydrothermally induced quartz growth

2017

Abstract Mineral precipitations are a common feature and limitation of initially open, permeable rock fractures by forming sealing structures or secondary roughness in open voids. Hence, the objective of this numerical study is the evaluation of hydraulic properties of fractures sealed by hydrothermally induced needle and compact quartz growth. Phase-field models of progressive syntaxial and idiomorphic quartz growth are implemented into a fluid flow simulation solving the Navier–Stokes equation. Flow simulations for both quartz types indicate an obvious correlation between changes in permeability, fracture properties (e.g. aperture, relative roughness and porosity) and crystal growth behav…

Study of the defects in La3Ta0.5Ga5.5O14 single crystals

2016

Abstract Defects that are formed during crystal growth pose a serious obstacle for potential application of La 3 Ga 5.5 Ta 0.5 O 14 (LGT) as a laser or piezoelectric crystal. We have performed the study of the defects origin in LGT crystals grown in different atmospheres using optical, EPR and time-resolved luminescence characterization methods. The absorption bands detected in the transparency region at 290, 360 and 490 nm ( T =300 K) demonstrate different dependence on crystal annealing in vacuum and air. EPR analysis demonstrated that the defects responsible for these bands are non-paramagnetic. X-ray irradiation results in hole trapping by oxygen ions thus forming O − centers perturbed …

Spontaneous intercalation of Ga and In bilayers during plasma-assisted molecular beam epitaxy growth of GaN on graphene on SiC

2019

The formation of a self-limited metallic bilayer is reported during the growth of GaN by plasma-assisted molecular beam epitaxy on graphene on (0001) SiC. Depending on growth conditions, this layer may consist of either Ga or In, which gets intercalated between graphene and the SiC surface. Diffusion of metal atoms is eased by steps at SiC surface and N plasma induced defects in the graphene layer. Energetically favorable wetting of the (0001) SiC surface by Ga or In is tentatively assigned to the breaking of covalent bonds between (0001) SiC surface and carbon buffer layer. As a consequence, graphene doping and local strain/doping fluctuations decrease. Furthermore, the presence of a metal…

Dielectric and magnetic properties of CdMoO4:Gd3+ single crystal

2014

Broadband dielectric spectroscopy and magnetic measurements provide experimental evidence that the CdMoO4:Gd 3+ single crystal is the paramagnet with low relative dielectric permittivity (er � 8), which slightly depends on the temperature and frequencies. Magnetization with zero coercivity and remanence is almost a universal function of l0H/T, characterizing superparamagnetic-like behavior. These results are being considered in a framework of the random distribution of the Ga 3+ ions in the tetragonal structure.

Evaporation-induced assembly of colloidal crystals

2018

Colloidal crystals are often prepared by evaporation from solution, and there is considerable interest to link the processing conditions to the crystal morphology and quality. Here, we study the evaporation-induced assembly of colloidal crystals using massive-scale nonequilibrium molecular dynamics simulations. We apply a recently developed machine-learning technique to characterize the assembling crystal structures with unprecedented microscopic detail. In agreement with previous experiments and simulations, faster evaporation rates lead to earlier onset of crystallization and more disordered surface structures. Surprisingly, we find that collective rearrangements of the bulk crystal durin…