scholarly journals Calphad Modeling of LRO and SRO Using ab initio Data

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 998
Author(s):  
Masanori Enoki ◽  
Bo Sundman ◽  
Marcel H. F. Sluiter ◽  
Malin Selleby ◽  
Hiroshi Ohtani
Keyword(s):  
Experimental Data ◽  
Dft Calculations ◽  
Short Range ◽  
State Of The Art ◽  
Model Parameters ◽  
Experimental Uncertainty ◽  
Calphad Technique ◽  
Calphad Modeling ◽  
Short Range Ordering ◽  
Long Range Ordering

Results from DFT calculations are in many cases equivalent to experimental data. They describe a set of properties of a phase at a well-defined composition and temperature, T, most often at 0 K. In order to be practically useful in materials design, such data must be fitted to a thermodynamic model for the phase to allow interpolations and extrapolations. The intention of this paper is to give a summary of the state of the art by using the Calphad technique to model thermodynamic properties and calculate phase diagrams, including some models that should be avoided. Calphad models can decribe long range ordering (LRO) using sublattices and there are model parameters that can approximate short range ordering (SRO) within the experimental uncertainty. In addition to the DFT data, there is a need for experimental data, in particular, for the phase diagram, to determine the model parameters. Very small differences in Gibbs energy of the phases, far smaller than the uncertainties in the DFT calculations, determine the set of stable phases at varying composition and T. Thus, adjustment of the DFT results is often needed in order to obtain the correct set of stable phases.

COMPARISON OF THE NMR AND NEUTRON SCATTERING EXPERIMENTS ON CUPRATES WITH NONMAGNETIC IMPURITIES

2000 ◽  
Vol 14 (29n31) ◽  
pp. 3374-3379
Author(s):  
N. BULUT ◽  
U. YAZ
Keyword(s):  
Experimental Data ◽  
Neutron Scattering ◽  
Short Range ◽  
Model Parameters ◽  
Extended Form ◽  
Impurity Potential ◽  
Pure System ◽  
Nonmagnetic Impurities ◽  
Antiferromagnetic Correlations

The NMR and neutron scattering experiments on YBa 2 Cu 3 O 7 with Li and Zn impurities are compared using a simple framework exhibiting short-range antiferromagnetic correlations. The model parameters are determined by fitting the NMR rate [Formula: see text] of the pure system, and the effective impurity potential is approximated by a static extended form. The results of the calculations are compared with the experimental data, and their implications are discussed.

Temperature dependence of the resistivity of Hg3–δAsF6

1982 ◽  
Vol 60 (9) ◽  
pp. 1348-1357 ◽  
Author(s):  
E. Batalla ◽  
W. R. Datars
Keyword(s):  
Fermi Surface ◽  
Temperature Dependence ◽  
Electron Scattering ◽  
Short Range ◽  
Linear Chain ◽  
Three Dimensional ◽  
One Dimensional ◽  
Anisotropic Superconductor ◽  
Short Range Ordering ◽  
Long Range Ordering

The resistivity of the linear-chain mercury compound Hg3–δAsF6 is reported in the temperature range 1.4–300 K. Electron scattering by one-dimensional and three-dimensional phonons on a cylindrical Fermi surface is used to calculate the temperature dependence of the resistivity which agrees with measurements of the resistivity between 4.2 and 90 K. The resistivity is determined by the Montgomery method which is extended to the case when electrical probes are not at the corners of a sample. The anisotropy ρc/ρa of the resistivity is in the range 95 ± 10 between 40 and 180 K. It is explained by a 1.4% undulation along the Fermi surface cylinders. Changes in the anisotropy give evidence of three-dimensional, long-range ordering at 120 K and short-range ordering of the mercury chains between 180 and 200 K reported previously. Hysteresis in the resistivity shows an unusual transition at 217 ± 3 K which is evident only upon cooling samples. There is no evidence of zero, c-axis resistivity below 4.1 K to support the suggestion that Hg3–δAsF6 is an anisotropic superconductor.

Thermodynamics of mixing and ordering in the diopside–jadeite system: II. A polynomial fit to the CVM results

2002 ◽  
Vol 66 (4) ◽  
pp. 537-545 ◽  
Author(s):  
V. L. Vinograd
Keyword(s):  
Solid Solution ◽  
Free Energy ◽  
Short Range ◽  
Gaussian Functions ◽  
Equilibrium Computation ◽  
Polynomial Fit ◽  
Short Range Ordering ◽  
Thermodynamics Of Mixing ◽  
Long Range Ordering ◽  
The Relationship

AbstractIn Part I (Vinograd, 2002) the relationship between temperature, composition and free energy of the diopside–jadeite solid solution was described using a CVM model. Here the same relationship is described using a combination of Redlich-Kister (RK) polynomials and Gaussian functions. The use of the Gaussians permits an accurate description of the free energy dip centred at Jd50, which is caused by the long-range ordering, while the effect of the short-range ordering can be easily modelled using the RK polynomial The simplified RK-Gaussian description is extended to the three-component diopside–jadeite–hedenbergite solid solution. The polynomial description permits an easy incorporation of the derived activity-composition relations into phase-equilibrium computation software.

Spontaneous Lateral Composition Modulation in III-V Semiconductor Alloys

MRS Bulletin ◽  
1997 ◽  
Vol 22 (7) ◽  
pp. 38-43 ◽  
Author(s):  
J. Mirecki Millunchick ◽  
R.D. Twesten ◽  
S.R. Lee ◽  
D.M. Follstaedt ◽  
E.D. Jones ◽  
...  
Keyword(s):  
Long Range ◽  
High Speed ◽  
Short Range ◽  
Carrier Mobility ◽  
Alloy System ◽  
Semiconductor Alloys ◽  
Chemical Ordering ◽  
Short Range Ordering ◽  
Device Structures ◽  
Long Range Ordering

The application of III-V semiconductor alloys in device structures is of importance for high-speed microelectronics and optoelectronics. These alloys have allowed the device engineer to tailor material parameters such as the bandgap and carrier mobility to the need of the device by altering the alloy composition. When using ternary or quaternary materials, the device designer presumes that the alloy is completely disordered, without any correlation between the atoms on the cation (anion) sublattice. However the thermodynamics of the alloy system often produce material that has some degree of macroscopic or microscopic ordering. Short-range ordering occurs when atoms adopt correlated neighboring positions over distances of the order of a few lattice spacings. This can be manifested as the preferential association of like atoms, as in clustering, or of unlike atoms, as in chemical ordering (e.g., CuPt ordering). Long-range ordering occurs over many tens of lattice spacings, as in the case of phase separation. In either short-range or long-range ordering, the band structure and the crystal symmetry are greatly altered. Therefore it is absolutely critical that the mechanisms be fully understood to prevent ordering when necessary or to exploit it when possible.

Parameter Determination for Chloride and Tritium Transport in Undisturbed Lysimeters during Steady Flow

1992 ◽  
Vol 23 (2) ◽  
pp. 89-104 ◽  
Author(s):  
Ole H. Jacobsen ◽  
Feike J. Leij ◽  
Martinus Th. van Genuchten
Keyword(s):  
Experimental Data ◽  
Unsaturated Flow ◽  
Transport Model ◽  
Time Moment ◽  
Breakthrough Curves ◽  
Coarse Sand ◽  
Retardation Factor ◽  
Parameter Determination ◽  
Model Parameters ◽  
Water Fraction

Breakthrough curves of Cl and 3H2O were obtained during steady unsaturated flow in five lysimeters containing an undisturbed coarse sand (Orthic Haplohumod). The experimental data were analyzed in terms of the classical two-parameter convection-dispersion equation and a four-parameter two-region type physical nonequilibrium solute transport model. Model parameters were obtained by both curve fitting and time moment analysis. The four-parameter model provided a much better fit to the data for three soil columns, but performed only slightly better for the two remaining columns. The retardation factor for Cl was about 10 % less than for 3H2O, indicating some anion exclusion. For the four-parameter model the average immobile water fraction was 0.14 and the Peclet numbers of the mobile region varied between 50 and 200. Time moments analysis proved to be a useful tool for quantifying the break through curve (BTC) although the moments were found to be sensitive to experimental scattering in the measured data at larger times. Also, fitted parameters described the experimental data better than moment generated parameter values.

scholarly journals Revisiting the Analysis of the Isochronous Mass Measurements of Uranium Fission Fragments at the ESR

2020 ◽  
Vol 227 ◽  
pp. 02012
Author(s):  
R. S. Sidhu ◽  
R. J. Chen ◽  
Yu. A Litvinov ◽  
Y. H. Zhang ◽  
Keyword(s):  
Experimental Data ◽  
Data Analysis ◽  
State Of The Art ◽  
Fission Products ◽  
Mass Measurements ◽  
Fission Fragments ◽  
Uranium Fission

The re-analysis of experimental data on mass measurements of ura- nium fission products obtained at the ESR in 2002 is discussed. State-of-the-art data analysis procedures developed for such measurements are employed.

scholarly journals Modelling the Inflation and Elastic Instabilities of Rubber-Like Spherical and Cylindrical Shells Using a New Generalised Neo-Hookean Strain Energy Function

2021 ◽  
Author(s):  
Afshin Anssari-Benam ◽  
Andrea Bucchi ◽  
Giuseppe Saccomandi
Keyword(s):  
Experimental Data ◽  
Energy Function ◽  
Limit Point ◽  
Strain Energy ◽  
Cylindrical Shells ◽  
Strain Energy Function ◽  
Model Parameters ◽  
Wide Range ◽  
Cylindrical Tubes ◽  
Gent Model

AbstractThe application of a newly proposed generalised neo-Hookean strain energy function to the inflation of incompressible rubber-like spherical and cylindrical shells is demonstrated in this paper. The pressure ($P$ P ) – inflation ($\lambda $ λ or $v$ v ) relationships are derived and presented for four shells: thin- and thick-walled spherical balloons, and thin- and thick-walled cylindrical tubes. Characteristics of the inflation curves predicted by the model for the four considered shells are analysed and the critical values of the model parameters for exhibiting the limit-point instability are established. The application of the model to extant experimental datasets procured from studies across 19th to 21st century will be demonstrated, showing favourable agreement between the model and the experimental data. The capability of the model to capture the two characteristic instability phenomena in the inflation of rubber-like materials, namely the limit-point and inflation-jump instabilities, will be made evident from both the theoretical analysis and curve-fitting approaches presented in this study. A comparison with the predictions of the Gent model for the considered data is also demonstrated and is shown that our presented model provides improved fits. Given the simplicity of the model, its ability to fit a wide range of experimental data and capture both limit-point and inflation-jump instabilities, we propose the application of our model to the inflation of rubber-like materials.

Emulation of short-range ordering within the Compound Energy Formalism: Application to the calcite-magnesite solid solution

Calphad ◽  
2019 ◽  
Vol 64 ◽  
pp. 115-125 ◽  
Author(s):  
Xin Liu ◽  
Victor L. Vinograd ◽  
Sergii Nichenko ◽  
Dmitrii A. Kulik ◽  
Xiancai Lu ◽  
...  
Keyword(s):  
Solid Solution ◽  
Short Range ◽  
Compound Energy Formalism ◽  
Short Range Ordering

Practical Astronomy Education at the National University of Singapore (NUS)

2019 ◽  
Vol 01 (01) ◽  
pp. 1950004
Author(s):  
A. Yang ◽  
S. C. Cindy Ng ◽  
Q. Leong ◽  
M. H. Tan ◽  
P. Agarwal ◽  
...  
Keyword(s):  
Experimental Data ◽  
General Education ◽  
Scientific Theory ◽  
State Of The Art ◽  
Educational Institutions ◽  
Astronomy Education ◽  
National University ◽  
Robotic Telescope ◽  
Astronomy And Astrophysics

Singapore is not known for astronomy research. However, the interest in astronomy has grown since the 1990s, when more educational institutions and observatories were built to equip students with the skills and knowledge in astronomy. The National University of Singapore (NUS) currently has a strong and rigorous astronomy and astrophysics programme that leads to an astrophysics specialization within the physics B.Sc. degree as well as four general education modules in astronomy and astrophysics. As experimental data is the final arbiter of any scientific theory, we emphasize the practical aspects of astronomy in this programme. We also have a state-of-the-art observatory equipped with a robotic telescope and a planetarium for tutorials. This paper outlines the philosophy, pedagogy and approach of how our NUS team has achieved a very successful undergraduate astronomy and astrophysics for aspiring Singaporean youth.

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