Coarse-grained modeling of crystal growth and polymorphism of a model pharmaceutical molecule

Soft Matter ◽  
2016 ◽  
Vol 12 (39) ◽  
pp. 8246-8255 ◽  
Author(s):  
Taraknath Mandal ◽  
Ryan L. Marson ◽  
Ronald G. Larson
Keyword(s):  
Crystal Growth ◽  
Coarse Grained

scholarly journals Episodes of fast crystal growth in pegmatites

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Patrick R. Phelps ◽  
Cin-Ty A. Lee ◽  
Douglas M. Morton
Keyword(s):  
Crystal Growth ◽  
Trace Element ◽  
Boundary Layers ◽  
Growth Rates ◽  
Coarse Grained ◽  
Initial Growth ◽  
Quartz Crystals ◽  
Kinetic Effects ◽  
High Reynolds ◽  
Miarolitic Cavities

Abstract Pegmatites are shallow, coarse-grained magmatic intrusions with crystals occasionally approaching meters in length. Compared to their plutonic hosts, pegmatites are thought to have cooled rapidly, suggesting that these large crystals must have grown fast. Growth rates and conditions, however, remain poorly constrained. Here we investigate quartz crystals and their trace element compositions from miarolitic cavities in the Stewart pegmatite in southern California, USA, to quantify crystal growth rates. Trace element concentrations deviate considerably from equilibrium and are best explained by kinetic effects associated with rapid crystal growth. Kinetic crystal growth theory is used to show that crystals accelerated from an initial growth rate of 10−6–10−7 m s−1 to 10−5–10−4 m s−1 (10-100 mm day−1 to 1–10 m day−1), indicating meter sized crystals could have formed within days, if these rates are sustained throughout pegmatite formation. The rapid growth rates require that quartz crystals grew from thin (micron scale) chemical boundary layers at the fluid-crystal interfaces. A strong advective component is required to sustain such thin boundary layers. Turbulent conditions (high Reynolds number) in these miarolitic cavities are shown to exist during crystallization, suggesting that volatile exsolution, crystallization, and cavity generation occur together.

COMPUTER MODEL OF A LYSOZYME CRYSTAL GROWTH WITH/WITHOUT NANOTEMPLATE — A COMPARISON

2006 ◽  
Vol 17 (09) ◽  
pp. 1359-1366 ◽  
Author(s):  
J. SIÓDMIAK ◽  
A. GADOMSKI ◽  
E. PECHKOVA ◽  
C. NICOLINI
Keyword(s):  
Computer Simulation ◽  
Monte Carlo ◽  
Crystal Growth ◽  
Computer Model ◽  
Monte Carlo Technique ◽  
Coarse Grained ◽  
Langmuir Blodgett ◽  
Lattice Monte Carlo ◽  
Experimental Findings ◽  
Lysozyme Crystal

The results of a computer simulation of the lysozyme crystal growth influenced by monomer and tetramer (aggregate) units are discussed. A very recently introduced computer model of biopolymer crystal growth and aggregation is based on the 2D lattice Monte Carlo technique and the coarse-grained HP approximation of the lysozyme monomeric unit. Acceleration of the lysozyme crystal growth by a factor of 4/3, based on the 2AUB (PDB ID) lysozyme unit, obtained from the Langmuir–Blodgett nanotemplate method, has clearly been confirmed by means of the proposed computer simulation. It is concluded that the aggregates (tetramers) involving 2AUB lysozyme crystal growth can be expected to be slightly accelerated when compared to its monomer-based (PDB ID: 193L) counterpart, which is in excellent accord with very recent experimental findings of the emerging applied science called protein nanocrystallography.

scholarly journals CONTROLE DO MINÉRIO DE ESPODUMÊNIO EM PEGMATITOS DA MINA DA CACHOEIRA, ARAÇUAÍ, MG

2013 ◽  
Author(s):  
Júlio Cezar Pimenta Romeiro ◽  
Antônio Carlos Pedrosa-Soares
Keyword(s):  
Grain Size ◽  
Crystal Growth ◽  
Structural Control ◽  
Crystal Size ◽  
Mine Planning ◽  
Coarse Grained ◽  
High Angle ◽  
The North ◽  
Group A ◽  
Different Depths

The focused pegmatites belong to the Cachoeira Group, a spodumene-rich pegmatite population ofthe Araçuaí Pegmatite District, located in the north region of the Eastern Brazilian PegmatiteProvince. The Cachoeira Mine (CBL-Companhia Brasileira de Lítio) is located in the low valley ofthe Piauí River, east of Araçuaí town, Minas Gerais. The structural control of the pegmatites andrelated variations in spodumene grain size are important factors for mine planning. The pegmatitesof the Cachoeira Mine are non-zoned bodies with very few and small replacement pockets. Theyintruded along two different NE-striking surfaces of medium- to high-angle dip: the NW-dippingschistosity and the SE-dipping fracture cleavage. Systematic measurements show that the generalaverage size of spodumene crystals decreases with depth (i.e., the deeper the pegmatite segment, thesmaller the crystal size), but spodumene modal contents remain similar in different depths. Enrichmentin coarse-grained spodumene crystals occurs in shallow-dipping pegmatite segments. The increasingin spodumene crystal size, from lower to upper depths, can be related to decreasing in viscosity of thesilicate melt in response to accumulation of rising aqueous fluids towards the top of the pegmatite.The same effect can be expected for places of fluid swimming, such as the shallow-dipping pegmatitesegments. Fluids, like H2O and F, act by lowering the viscosity that, in turn, assists crystal growth. K/Rb and K/Ba ratios obtained from microcline crystals, associated to the spodumene, decrease graduallyfrom the bottom to the top of the pegmatites. Such increasing (to the top) in Rb and Ba also suggestsfluid enrichment in the same way of the increasing size of spodumene crystals.

The Alteration of the Pore Spaces in Sandstones

1973 ◽  
Vol 31 ◽  
pp. 210-211
Author(s):  
R. E. Ferrell ◽  
G. G. Paulson
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
The Other ◽  
Coarse Grained ◽  
Depositional Fabric ◽  
Soluble Components ◽  
Scanning Electron ◽  
Shape And Size

The pore spaces in sandstones are the result of the original depositional fabric and the degree of post-depositional alteration that the rock has experienced. The largest pore volumes are present in coarse-grained, well-sorted materials with high sphericity. The chief mechanisms which alter the shape and size of the pores are precipitation of cementing agents and the dissolution of soluble components. Each process may operate alone or in combination with the other, or there may be several generations of cementation and solution.The scanning electron microscope has ‘been used in this study to reveal the morphology of the pore spaces in a variety of moderate porosity, orthoquartzites.

On the Origin of the Microscystalline Structure in Rapidly Solidified IN-100 Powder

1977 ◽  
Vol 35 ◽  
pp. 260-261
Author(s):  
J. M. Walsh ◽  
K. P. Gumz ◽  
J. C. Whittles ◽  
B. H. Kear
Keyword(s):  
The Other ◽  
Coarse Grained ◽  
Microcrystalline Structure ◽  
Routine Examination ◽  
Atomization Process ◽  
Centrifugal Atomization ◽  
Splat Quenching ◽  
Powder Particles ◽  
Dendritic Microstructures ◽  
Rapidly Solidified

During a routine examination of the microstructure of rapidly solidified IN-100 powder, produced by a newly-developed centrifugal atomization process1, essentially two distinct types of microstructure were identified. When a high melt superheat is maintained during atomization, the powder particles are predominantly coarse-grained, equiaxed or columnar, with distinctly dendritic microstructures, Figs, la and 4a. On the other hand, when the melt superheat is reduced by increasing the heat flow to the disc of the rotary atomizer, the powder particles are predominantly microcrystalline in character, with typically one dendrite per grain, Figs, lb and 4b. In what follows, evidence is presented that strongly supports the view that the unusual microcrystalline structure has its origin in dendrite erosion occurring in a 'mushy zone' of dynamic solidification on the disc of the rotary atomizer.The critical observations were made on atomized material that had undergone 'splat-quenching' on previously solidified, chilled substrate particles.

Montmorillonite Dendrites

1974 ◽  
Vol 32 ◽  
pp. 454-455
Author(s):  
Necip Güven ◽  
Rodney W. Pease
Keyword(s):  
Crystal Growth ◽  
Growth Mechanism ◽  
Growth Front ◽  
Morphological Features ◽  
Dendritic Crystal ◽  
Crystal Growth Mechanism

Morphological features of montmorillonite aggregates in a large number of samples suggest that they may be formed by a dendritic crystal growth mechanism (i.e., tree-like growth by branching of a growth front).

TEM and cathodoluminescence of precipitates in II-VI semiconductors

1988 ◽  
Vol 46 ◽  
pp. 488-489
Author(s):  
Joanna L. Batstone
Keyword(s):  
Crystal Growth ◽  
Band Gap ◽  
Local Strain ◽  
Wide Band ◽  
Optoelectronic Device ◽  
Wide Band Gap ◽  
Bulk Crystal Growth ◽  
Transmission Electron ◽  
Device Applications ◽  
Stoichiometry Control

Interest in II-VI semiconductors centres around optoelectronic device applications. The wide band gap II-VI semiconductors such as ZnS, ZnSe and ZnTe have been used in lasers and electroluminescent displays yielding room temperature blue luminescence. The narrow gap II-VI semiconductors such as CdTe and HgxCd1-x Te are currently used for infrared detectors, where the band gap can be varied continuously by changing the alloy composition x.Two major sources of precipitation can be identified in II-VI materials; (i) dopant introduction leading to local variations in concentration and subsequent precipitation and (ii) Te precipitation in ZnTe, CdTe and HgCdTe due to native point defects which arise from problems associated with stoichiometry control during crystal growth. Precipitation is observed in both bulk crystal growth and epitaxial growth and is frequently associated with segregation and precipitation at dislocations and grain boundaries. Precipitation has been observed using transmission electron microscopy (TEM) which is sensitive to local strain fields around inclusions.

STM studies of crystal growth

1991 ◽  
Vol 49 ◽  
pp. 374-375
Author(s):  
M. G. Lagally
Keyword(s):  
Crystal Growth ◽  
Molecular Beam ◽  
Chemical Vapor ◽  
Sputter Deposition ◽  
Field Of View ◽  
Scanning Tunneling ◽  
Wide Field ◽  
Tunneling Microscopy ◽  
Wide Field Of View ◽  
The One

It has been recognized since the earliest days of crystal growth that kinetic processes of all Kinds control the nature of the growth. As the technology of crystal growth has become ever more refined, with the advent of such atomistic processes as molecular beam epitaxy, chemical vapor deposition, sputter deposition, and plasma enhanced techniques for the creation of “crystals” as little as one or a few atomic layers thick, multilayer structures, and novel materials combinations, the need to understand the mechanisms controlling the growth process is becoming more critical. Unfortunately, available techniques have not lent themselves well to obtaining a truly microscopic picture of such processes. Because of its atomic resolution on the one hand, and the achievable wide field of view on the other (of the order of micrometers) scanning tunneling microscopy (STM) gives us this opportunity. In this talk, we briefly review the types of growth kinetics measurements that can be made using STM. The use of STM for studies of kinetics is one of the more recent applications of what is itself still a very young field.

Cristal-growth dynamics of n-doped gaAs

1992 ◽  
Vol 50 (2) ◽  
pp. 1544-1545
Author(s):  
Pham V. Huong ◽  
Stéphanie Bouchet ◽  
Jean-Claude Launay
Keyword(s):  
Crystal Growth ◽  
Spatial Resolution ◽  
Epitaxial Layer ◽  
Outer Surface ◽  
Gaas Substrate ◽  
Structural Modification ◽  
Growth Dynamics ◽  
Argon Laser ◽  
High Anisotropy ◽  
Crystal Gaas

Microstructure of epitaxial layers of doped GaAs and its crystal growth dynamics on single crystal GaAs substrate were studied by Raman microspectroscopy with a Dilor OMARS instrument equipped with a 1024 photodiode multichannel detector and a ion-argon laser Spectra-Physics emitting at 514.5 nm.The spatial resolution of this technique, less than 1 μm2, allows the recording of Raman spectra at several spots in function of thickness, from the substrate to the outer deposit, including areas around the interface (Fig.l).The high anisotropy of the LO and TO Raman bands is indicative of the orientation of the epitaxial layer as well as of the structural modification in the deposit and in the substrate at the interface.With Sn doped, the epitaxial layer also presents plasmon in Raman scattering. This fact is already very well known, but we additionally observed that its frequency increases with the thickness of the deposit. For a sample with electron density 1020 cm-3, the plasmon L+ appears at 930 and 790 cm-1 near the outer surface.

Correlation between dislocation, grain boundary and interface of duplex SS in stress corrosion cracking(SCC)

1990 ◽  
Vol 48 (4) ◽  
pp. 928-929
Author(s):  
Wang Zheng-fang ◽  
Z.F. Wang
Keyword(s):  
Stainless Steel ◽  
Thermal Cycle ◽  
Secondary Phase ◽  
Corrosion Cracking ◽  
Coarse Grained ◽  
Test Environment ◽  
Fine Grained ◽  
Evaluation Test ◽  
Welding Thermal Cycle ◽  
Micro Analysis

The main purpose of this study highlights on the evaluation of chloride SCC resistance of the material,duplex stainless steel,OOCr18Ni5Mo3Si2 (18-5Mo) and its welded coarse grained zone(CGZ).18-5Mo is a dual phases (A+F) stainless steel with yield strength:512N/mm2 .The proportion of secondary Phase(A phase) accounts for 30-35% of the total with fine grained and homogeneously distributed A and F phases(Fig.1).After being welded by a specific welding thermal cycle to the material,i.e. Tmax=1350°C and t8/5=20s,microstructure may change from fine grained morphology to coarse grained morphology and from homogeneously distributed of A phase to a concentration of A phase(Fig.2).Meanwhile,the proportion of A phase reduced from 35% to 5-10°o.For this reason it is known as welded coarse grained zone(CGZ).In association with difference of microstructure between base metal and welded CGZ,so chloride SCC resistance also differ from each other.Test procedures:Constant load tensile test(CLTT) were performed for recording Esce-t curve by which corrosion cracking growth can be described, tf,fractured time,can also be recorded by the test which is taken as a electrochemical behavior and mechanical property for SCC resistance evaluation. Test environment:143°C boiling 42%MgCl2 solution is used.Besides, micro analysis were conducted with light microscopy(LM),SEM,TEM,and Auger energy spectrum(AES) so as to reveal the correlation between the data generated by the CLTT results and micro analysis.

Sign in / Sign up

Export Citation Format

Share Document