scholarly journals Crystallisation and polymorph selection in active Brownian particles

2021 ◽  
Vol 44 (9) ◽  
Author(s):  
Fergus J. Moore ◽  
C. Patrick Royall ◽  
Tanniemola B. Liverpool ◽  
John Russo
Keyword(s):  
Numerical Simulation ◽  
Growth Rate ◽  
Hard Spheres ◽  
Stacking Faults ◽  
Nucleation And Growth ◽  
Crystal Growth Rate ◽  
Growth Regime ◽  
Brownian Particles ◽  
Polymorph Selection ◽  
Weak Activity

AbstractWe explore crystallisation and polymorph selection in active Brownian particles with numerical simulation. In agreement with previous work (Wysocki et al. in Europhys Lett 105:48004, 2014), we find that crystallisation is suppressed by activity and occurs at higher densities with increasing Péclet number ($${ Pe }$$ Pe ). While the nucleation rate decreases with increasing activity, the crystal growth rate increases due to the accelerated dynamics in the melt. As a result of this competition, we observe the transition from a nucleation and growth regime at high $${ Pe }$$ Pe to “spinodal nucleation” at low $${ Pe }$$ Pe . Unlike the case of passive hard spheres, where preference for FCC over HCP polymorphs is weak, activity causes the annealing of HCP stacking faults, thus strongly favouring the FCC symmetry at high $${ Pe }$$ Pe . When freezing occurs more slowly, in the nucleation and growth regime, this tendency is much reduced and we see a trend towards the passive case of little preference for either polymorph.

Phase separation in undercooled molten Pd80Si20: Part I

1999 ◽  
Vol 14 (9) ◽  
pp. 3653-3662 ◽  
Author(s):  
K. L. Lee ◽  
H. W. Kui
Keyword(s):  
Growth Rate ◽  
Phase Separation ◽  
Crystal Growth ◽  
Grain Refinement ◽  
Crystallization Temperature ◽  
Sharp Decrease ◽  
Nucleation And Growth ◽  
Crystal Growth Rate ◽  
Large Undercooling ◽  
Kinetic Crystallization

Three different kinds of morphology are found in undercooled Pd80Si20, and they dominate at different undercooling regimens ΔT, defined as ΔT = T1 – Tk, where T1 is the liquidus of Pd80Si20 and Tk is the kinetic crystallization temperature. In the small undercooling regimen, i.e., for ΔT ≤ 190 K, the microstructures are typically dendritic precipitation with a eutecticlike background. In the intermediate undercooling regimen, i.e., for 190 ≤ ΔT ≤ 220 K, spherical morphologies, which arise from nucleation and growth, are identified. In addition, Pd particles are found throughout an entire undercooled specimen. In the large undercooling regimen, i.e., for ΔT ≥ 220 K, a connected structure composed of two subnetworks is found. A sharp decrease in the dimension of the microstructures occurs from the intermediate to the large undercooling regimen. Although the crystalline phases in the intermediate and the large undercooling regimens are the same, the crystal growth rate is too slow to bring about the occurrence of grain refinement. Combining the morphologies observed in the three undercooling regimens and their crystallization behaviors, we conclude that phase separation takes place in undercooled molten Pd80Si20.

Numerical Simulation of Point Defect Distributions in a Growing Czochralski Silicon Crystal in Response to an Abrupt Change in the Growth Conditions

1995 ◽  
Vol 378 ◽  
Author(s):  
W. Wijaranakula ◽  
Q. S. Zhang ◽  
K. Takano ◽  
H. Yamagishi
Keyword(s):  
Numerical Simulation ◽  
Growth Rate ◽  
Crystal Growth ◽  
Point Defect ◽  
Flow Pattern ◽  
Abrupt Change ◽  
Silicon Crystal ◽  
Crystal Growth Rate ◽  
Rate Theory ◽  
Czochralski Silicon

AbstractNumerical simulation of point defect distributions in a growing Czochralski silicon crystal with an abrupt change in the crystal growth rate from 1.0 to 0.4 mm/min was performed. The result was fitted to the experimental data for the flow pattern defects obtained from a crystal grown under simulated conditions. From the simulation result, it was observed that the axial temperature distribution shifts slightly upwards as a result of the growth rate reduction. Based upon the argument that the flow pattern defects are of vacancy-type, it is proposed that the generation rate of the flow pattern defects during crystal growth can be described by the classical nucleation rate theory proposed by Becker [Proc.Phys.Soc., 52, 71(1940)]. In addition, it is suggested that the vacancy concentration in the flow pattern defects depends upon the reaction time between the silicon interstitials and the flow pattern defects and thus the crystal growth rate.

Experimental Measurements of Nucleation Frequency and Crystal Growth Rate in Pd-Cu-Ni-P Metallic Glass

1998 ◽  
Vol 554 ◽  
Author(s):  
Nobuyuki Nishiyama ◽  
Akihisa Inoue
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Annealing Temperature ◽  
Annealing Treatment ◽  
Nucleation And Growth ◽  
Crystal Growth Rate ◽  
Equilibrium Melting Temperature ◽  
Glass Forming ◽  
Mechanism And Kinetics ◽  
Kinetics Of

AbstractCrystallization mechanism and kinetics of a Pd40Cu30Ni10P20 glass was investigated in a wide temperature range from 603 (near the glass transition temperature) to 764 K (near the equilibrium melting temperature) by using an isothermal annealing treatment for nucleation and growth. The nucleus density (nv) is about 5 × 1013 nuclei/m3 and is independent of annealing temperature. Therefore, it is assumed that the crystallization of the alloy was dominated by heterogeneous nucleation due to “quenched-in nuclei”. On the other hand, the crystal growth rate (Uc) increases from 1.07 × 10− to 5.68 × 10−5 m/s with rising annealing temperature from 603 to 764 K. These values of Uc are 2–3 orders of magnitude larger than the calculated Uc on the basis of Classical Nucleation and Growth Theory (CNT). Furthermore, the glass-forming ability of the alloy will be discussed in the framework of the present results.

TEMPERATURE DEPENDENCE OF THE CRYSTAL GROWTH RATE IN POLAR GLACIERS

1987 ◽  
Vol 48 (C1) ◽  
pp. C1-661-C1-662 ◽  
Author(s):  
J. R. PETIT ◽  
P. DUVAL ◽  
C. LORIUS
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Temperature Dependence ◽  
Crystal Growth Rate

Comparison of copper sulphate pentahydrate growth rates determined by different methods

1990 ◽  
Vol 55 (7) ◽  
pp. 1691-1707 ◽  
Author(s):  
Miloslav Karel ◽  
Jiří Hostomský ◽  
Jaroslav Nývlt ◽  
Axel König
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Fluidized Bed ◽  
Growth Rates ◽  
Copper Sulphate ◽  
Crystal Growth Rate ◽  
Effect Of Temperature ◽  
Rotating Disc ◽  
Shape Factors ◽  
Data Treatment

Crystal growth rates of copper sulphate pentahydrate (CuSO4.5 H2O) determined by different authors and methods are compared. The methods included in this comparison are: (i) Measurement on a fixed crystal suspended in a streaming solution, (ii) measurement on a rotating disc, (iii) measurement in a fluidized bed, (iv) measurement in an agitated suspension. The comparison involves critical estimation of the supersaturation used in measurements, of shape factors used for data treatment and a correction for the effect of temperature. Conclusions are drawn for the choice of values to be specified when data of crystal growth rate measurements are published.

Continuous Precipitation of Lead Iodide

1994 ◽  
Vol 59 (7) ◽  
pp. 1503-1510
Author(s):  
Stanislav Žáček ◽  
Jaroslav Nývlt
Keyword(s):  
Growth Rate ◽  
Particle Size ◽  
Crystal Size ◽  
Crystal Growth Rate ◽  
Laboratory Model ◽  
Lead Iodide ◽  
Secondary Nucleation ◽  
Equimolar Ratio ◽  
Continuous Precipitation ◽  
The Mean

Lead iodide was precipitated from aqueous solutions of 0.015 - 0.1 M Pb(NO3)2 and 0.03 - 0.2 M KI in the equimolar ratio using a laboratory model of a stirred continuous crystallizer at 22 °C. After reaching the steady state, the PbI2 crystal size distribution was measured sedimentometrically and the crystallization kinetics was evaluated based on the mean particle size. Both the linear crystal growth rate and the nucleation rate depend on the specific output of the crystallizer. The system crystallization constant either points to a significant effect of secondary nucleation by the mechanism of contact of the crystals with the stirrer blade, or depends on the concentrations of the components added due to the micromixing mechanism.

Optical resolution of N-formylphenylalanine succeeds by crystal growth rate differences of diastereomeric salts

2007 ◽  
Vol 18 (2) ◽  
pp. 260-264 ◽  
Author(s):  
Laura Bereczki ◽  
Emese Pálovics ◽  
Petra Bombicz ◽  
György Pokol ◽  
Elemér Fogassy ◽  
...  
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Optical Resolution ◽  
Crystal Growth Rate ◽  
Diastereomeric Salts

Crystal-growth kinetics of protein single crystals along capillary tubes in the gel-acupuncture technique

1999 ◽  
Vol 55 (2) ◽  
pp. 577-580 ◽  
Author(s):  
Abel Moreno ◽  
Manuel Soriano-García
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Capillary Tube ◽  
Crystal Growth Rate ◽  
Equilibrium Studies ◽  
Acta Cryst ◽  
Average Growth ◽  
X Ray Crystallography ◽  
Growing Cell ◽  
Kinetics Of

In attempts to obtain protein crystals of a sufficient size for structural studies, lack of knowledge of the physicochemical properties of protein solutions and of their crystal-growth behaviour lead to a bottleneck for drug design as well as for X-ray crystallography. Most formal investigations on crystal-growth phenomena have been focused on equilibrium studies, where the protein is soluble, and on the kinetics of crystal growth, which is related to both nucleation and crystal-growth phenomena. The aim of this work is to measure the crystal-growth rate along a capillary tube used as a growing cell. These experiments were carried out using the gel-acupuncture technique [García-Ruiz et al. (1993). Mater. Res. Bull. 28, 541–546; García-Ruiz & Moreno (1994). Acta Cryst. D50, 484–490; García-Ruiz & Moreno (1997). J. Cryst. Growth, 178, 393–401]. Crystal-growth investigations took place using lysozyme and thaumatin I as standard proteins. The maximum average growth rate obtained in the lower part of the capillary tube was about 35 Å s−1 and the minimum average growing rate in the upper part of the capillary tube was about 8 Å s−1. The crystal-growth rate as a function of the supersaturation was experimentally estimated at a constant height along the capillary tube.

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