Prediction of metastable phase formation in an immiscible Cu–Cr system from interatomic potential and ab initio calculation

2003 ◽  
Vol 18 (10) ◽  
pp. 2300-2303 ◽  
Author(s):  
H. R. Gong ◽  
L. T. Kong ◽  
B. X. Liu
Keyword(s):  
Ab Initio ◽  
Interatomic Potential ◽  
Metastable Phase ◽  
The Body ◽  
Face Centered Cubic ◽  
The Face ◽  
Bcc Structure ◽  
Face Centered ◽  
Dynamics Simulations ◽  
Cr System

Ab initio calculation was performed to predict the structures, lattice constants, and cohesive energies of metastable Cu75Cr25 and Cu50Cr50 phases. An n-body Cu–Cr potential was derived through fitting to some ab initio calculated results and was capable of reproducing some intrinsic properties of the Cu–Cr system. Based on the derived potential, molecular dynamics simulations predicted that for a Cu100−xCrx alloy, the face-centered-cubic structure is more stable than the body-centered-cubic (bcc) one when 0 ≤ x ≤ 25, while the bcc structure becomes energetically favored when 25 < x ≤ 100. Interestingly, the predictions match well with the experimental observations.

scholarly journals Metastable–solid phase diagrams derived from polymorphic solidification kinetics

2021 ◽  
Vol 118 (9) ◽  
pp. e2017809118
Author(s):  
Babak Sadigh ◽  
Luis Zepeda-Ruiz ◽  
Jonathan L. Belof
Keyword(s):  
Large Scale ◽  
Solid Phase ◽  
Metastable Phase ◽  
Extensive Study ◽  
The Body ◽  
Face Centered Cubic ◽  
Nonequilibrium Processes ◽  
Solidification Kinetics ◽  
Face Centered ◽  
Dynamics Simulations

Nonequilibrium processes during solidification can lead to kinetic stabilization of metastable crystal phases. A general framework for predicting the solidification conditions that lead to metastable-phase growth is developed and applied to a model face-centered cubic (fcc) metal that undergoes phase transitions to the body-centered cubic (bcc) as well as the hexagonal close-packed phases at high temperatures and pressures. Large-scale molecular dynamics simulations of ultrarapid freezing show that bcc nucleates and grows well outside of the region of its thermodynamic stability. An extensive study of crystal–liquid equilibria confirms that at any given pressure, there is a multitude of metastable solid phases that can coexist with the liquid phase. We define for every crystal phase, a solid cluster in liquid (SCL) basin, which contains all solid clusters of that phase coexisting with the liquid. A rigorous methodology is developed that allows for practical calculations of nucleation rates into arbitrary SCL basins from the undercooled melt. It is demonstrated that at large undercoolings, phase selections made during the nucleation stage can be undone by kinetic instabilities amid the growth stage. On these bases, a solidification–kinetic phase diagram is drawn for the model fcc system that delimits the conditions for macroscopic grains of metastable bcc phase to grow from the melt. We conclude with a study of unconventional interfacial kinetics at special interfaces, which can bring about heterogeneous multiphase crystal growth. A first-order interfacial phase transformation accompanied by a growth-mode transition is examined.

MINIMAL KNOTTING NUMBERS

2009 ◽  
Vol 18 (08) ◽  
pp. 1159-1173 ◽  
Author(s):  
CASEY MANN ◽  
JENNIFER MCLOUD-MANN ◽  
RAMONA RANALLI ◽  
NATHAN SMITH ◽  
BENJAMIN MCCARTY
Keyword(s):  
The Body ◽  
Computer Algorithm ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Lattice ◽  
The Face ◽  
Face Centered ◽  
Body Centered Cubic Lattice

This article concerns the minimal knotting number for several types of lattices, including the face-centered cubic lattice (fcc), two variations of the body-centered cubic lattice (bcc-14 and bcc-8), and simple-hexagonal lattices (sh). We find, through the use of a computer algorithm, that the minimal knotting number in sh is 20, in fcc is 15, in bcc-14 is 13, and bcc-8 is 18.

Poisson's Ratio for Central-Force Polycrystals

1976 ◽  
Vol 31 (12) ◽  
pp. 1539-1542 ◽  
Author(s):  
H. M. Ledbetter
Keyword(s):  
Electron Energy ◽  
Poisson Ratio ◽  
The Body ◽  
Central Force ◽  
Face Centered Cubic ◽  
Polycrystalline Aggregate ◽  
Body Centered Cubic ◽  
The Face ◽  
Predicted Values ◽  
Face Centered

Abstract The Poisson ratio υ of a polycrystalline aggregate was calculated for both the face-centered cubic and the body-centered cubic cases. A general two-body central-force interatomatic potential was used. Deviations of υ from 0.25 were verified. A lower value of υ is predicted for the f.c.c. case than for the b.c.c. case. Observed values of υ for twenty-three cubic elements are discussed in terms of the predicted values. Effects of including volume-dependent electron-energy terms in the inter-atomic potential are discussed.

Formation of the cementite crystal in austenite by transformation of triangulated polyhedra

2019 ◽  
Vol 75 (3) ◽  
pp. 325-332
Author(s):  
V. S. Kraposhin ◽  
N. D. Simich-Lafitskiy ◽  
A. L. Talis ◽  
A. A. Everstov ◽  
M. Yu. Semenov
Keyword(s):  
Interatomic Potential ◽  
Mutual Orientation ◽  
Crystallographic Group ◽  
Mutual Transformation ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Orientation Relationships ◽  
The Face ◽  
Infinite Crystal ◽  
Face Centered

A mechanism is proposed for the nucleus formation at the mutual transformation of austenite and cementite crystals. The mechanism is founded on the interpretation of the considered structures as crystallographic tiling onto non-intersecting rods of triangulated polyhedra. A 15-vertex fragment of this linear substructure of austenite (cementite) can be transformed by diagonal flipping in a rhombus consisting of two adjacent triangular faces into a 15-vertex fragment of cementite (austenite). In the case of the mutual austenite–cementite transformation, the mutual orientation of the initial and final fragments coincides with the Thomson–Howell orientation relationships which are experimentally observed [Thompson & Howell (1988). Scr. Metall. 22, 229–233] in steels. The observed orientation relationship between f.c.c. austenite and cementite is determined by a crystallographic group–subgroup relationship between transformation participants and noncrystallographic symmetry which determines the transformation of triangulated clusters of transformation participants. Sequential fulfillment of diagonal flipping in the 15-vertex fragments of linear substructure (these fragments are equivalent by translation) ensures the austenite–cementite transformation in the whole infinite crystal. The energy barrier for diagonal flipping in the rhombus with iron atoms in its vertices has been calculated using the Morse interatomic potential and is found to be equal to 162 kJ mol−1 at the face-centered cubic–body-centered cubic transformation temperature in iron.

Investigation of Crystalline and Amorphous Forms of Aluminum and Its Alloys: Computational Modeling and Experiment

NANO ◽  
2018 ◽  
Vol 13 (03) ◽  
pp. 1850026
Author(s):  
Sergey Shityakov ◽  
Norbert Roewer ◽  
Carola Y. Förster ◽  
Hai T. Tran ◽  
Wenjun Cai ◽  
...  
Keyword(s):  
Metal Structure ◽  
Dislocation Nucleation ◽  
Al Alloys ◽  
Atomic Scale ◽  
Face Centered Cubic ◽  
Stress Strain ◽  
The Face ◽  
Tension And Compression ◽  
Face Centered ◽  
Dynamics Simulations

The purpose of this study is to investigate polycrystalline lattices of aluminum (Al) under the stress–strain conditions in all-atom molecular dynamics simulations and Al alloys using X-ray diffraction. Isothermal uniaxial tension and compression of these polycrystalline lattices showed no dislocation nucleation peaks, which correspond only to the Al monocrystal form. The best tensile and compressive resistance characteristics were observed for a material with the highest grain number ([Formula: see text]) due to the significant reduction of the face-centered cubic lattice in the metal structure. This process is mainly driven by the gradual elevation of the system’s kinetic energy. In the experiment, the amorphous Al alloys with higher manganese composition (20.5%) were investigated, matching the simulated amorphous structures. Overall, the results suggest that the increase in number of grains in Al lattices diminishes the stress–strain impact due to a more disordered atomic-scale (amorphous) metal composition.

SOLID HARMONICS AS BASIS FUNCTIONS FOR CUBIC CRYSTALS

1959 ◽  
Vol 37 (3) ◽  
pp. 350-361 ◽  
Author(s):  
D. D. Betts
Keyword(s):  
Basis Functions ◽  
The Body ◽  
New Method ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Crystals ◽  
Cubic Lattice ◽  
The Face ◽  
Face Centered ◽  
Body Centered Cubic Lattice

The various sets of basis functions useful in discussing cubic crystals must include sets of symmetrized combinations of powers of the co-ordinates ortho-gonalized over the cellular polyhedron. Such polynomials are here called solid harmonics. A study of the actual solid harmonics reveals the limitations of the spherical cell approximation. The solid harmonics can be used to develop a new method over the cellular polyhedron of the body-centered cubic lattice or of the face-centered cubic lattice.

MOLECULAR DYNAMICS SIMULATIONS OF STRUCTURAL PROPERTIES OF CuNi ALLOYS DURING THE COOLING PROCESS AT HIGH PRESSURE

2020 ◽  
Vol 65 (10) ◽  
pp. 10-17
Author(s):  
Thao Nguyen Thi ◽  
Giang Bui Thi Ha ◽  
Linh Tran Phan Thuy ◽  
Hop Nguyen Van ◽  
Chung Pham Do ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
High Pressure ◽  
Molecular Dynamics Simulations ◽  
Sudden Change ◽  
Face Centered Cubic ◽  
Cooling Process ◽  
Embedded Atom ◽  
The Face ◽  
Face Centered ◽  
Dynamics Simulations

Molecular dynamics simulations of Cu80Ni20 (Cu:Ni = 8:2) model with the size of 8788 atoms have been carried out to study the structure and mechanical behavior at high pressure of 45 GPa. The interactions between atoms of the system were calculated by the Quantum Sutton-Chen embedded-atom potentials. The crystallization has occurred during the cooling process with a cooling rate of 0.01 K\ps. The temperature range of the phase transition is determined based on the sudden change of atomic potential during the cooling process. There is also a sudden change in the number of individual atoms in the sample. At a temperature of 300 K, both Ni and Cu atoms are crystallized into the face-centered cubic (FCC) and the hexagonal close-packed (HCP) phases, respectively. The mechanical characteristics of the sample at 300 K were also analyzed in detail through the determination of elastic modulus, number of atoms, and void distribution during the tensile process.

The Crystal Structure of Pressure-Induced Phases of In2Te3and Ga2Te3

1992 ◽  
Vol 7 (2) ◽  
pp. 99-102 ◽  
Author(s):  
N.R. Serebryanaya
Keyword(s):  
Crystal Structure ◽  
Metastable Phase ◽  
Face Centered Cubic ◽  
Volume Changes ◽  
X Ray ◽  
The Face ◽  
Crystal Structure Transformation ◽  
Face Centered ◽  
Heating Up

AbstractPhase transitions were found with use of an in situX-ray anvil-type of apparatus with a boron annulus at pressures up to 12 GPa. The disordering of vacancies in the In sub-structure, or α→βtransition, was found in In2Te3at p > 1.9 GPa. The next transformation from the β-form into the Bi2Te3type of structure was observed in both sesquitellurides at 2.0 GPa and 5.0 GPa for In2TGe3and Ga2Te3respectively. The In2Te3metastable phase of the Bi2Te3resulted from heating up to 200° C at p > 4.0 GPa, and it remained in a normal condition on release of the pressure. The X-ray powder diffraction data of pressure-induced phases, volume changes and bulk modulus of both sesquitellurides are given. The compressibility anisotropy of the layer pressure-induced phase was observed. The mechanism of the crystal structure transformation from the face-centered cubic structure into the Bi2Te3type is proposed to be due to the displacement of atoms from the space diagonal of the cube [111] into [112]-cubic direction and the rhombohedral distortion of the angle between these directions.

The determination of solute atom displacements in mixed dumbbell interstitials for the face-centered-cubic lattice

1978 ◽  
Vol 56 (8) ◽  
pp. 1057-1070 ◽  
Author(s):  
N. Matsunami ◽  
M. L. Swanson ◽  
L. M. Howe
Keyword(s):  
Solute Atom ◽  
The Body ◽  
Continuum Approximation ◽  
Face Centered Cubic ◽  
Cubic Lattice ◽  
The Face ◽  
Solute Atoms ◽  
Face Centered ◽  
Small Solute

Interactions between irradiation-produced defects and solute atoms in metals have been investigated using the channeling technique. The interaction of interest in this investigation is the trapping of self interstitials by small solute atoms thus creating a [Formula: see text] mixed dumbbell, consisting of a host atom and a solute atom straddling a lattice site in the face-centered-cubic lattice. The displacement of solute atoms from lattice sites in the mixed dumbbell configuration was determined by comparing the experimentally observed normalized yields from solute atoms and from host atoms with the yields calculated analytically using the continuum approximation. The solute atoms in Al–Mn, Al–Cu, and Cu–Be mixed dumbbells were situated at 0.5 Å from the body-centered position, whereas the Ag atoms in Al–Ag dumbbells were 0.7 Å from this position. This result is consistent with the theoretical expectation that the smallest solute atoms are displaced the greatest amount in mixed dumbbells. In addition, experimentally obtained solute atom yields for [Formula: see text] and [Formula: see text] angular scans were compared with calculated scans. It was concluded that for large displacements of solute atoms into the flux peaking region, the analytical (continuum) calculation is a reliable method of determining solute atom displacements, either from the aligned yields or from the angular scans.

Some Characteristics of Al12Mo in Aluminum Annealed After Implantation with Molybdenum

1985 ◽  
Vol 51 ◽  
Author(s):  
L. D. Stephenson ◽  
J. Bentley ◽  
R. B. Benson ◽  
G. K. Hubler ◽  
P. A. Parrish
Keyword(s):  
Analytical Electron Microscopy ◽  
The Body ◽  
Face Centered Cubic ◽  
Granular Film ◽  
The Face ◽  
Face Centered ◽  
Surface Modified ◽  
Microscopy Techniques ◽  
Annealing Experiments ◽  
Precipitate Structure

ABSTRACTThe characteristics of A112Mo formed in aluminum annealed after implantation with selected maximum molybdenum concentrations were examined by analytical electron microscopy techniques. The A112MO was isolated as the only precipitate in the microstructure for maximum as-implanted molybdenum concentrations up to 11 atomic percent. The morphology of the A112MO can be selected by choosing the maximum as-implanted molybdenum level over the same concentration range. A predominantly lamellar A112MO precipitate structure formed when aluminum was annealed at 550°C after implantation with maximum molybdenum concentrations in the range of 3.3 - 4.4 at.%. The orientation of the body centered cubic (bcc) A112Mo precipitate with respect to the face centered cubic (fcc) matrix can be expressed as (123)p || (002)m and [301]p || [310]m. An explanation for the experimentally observed orientation relationship was developed based on the characteristic relationships between the bcc A112MO precipitate and the fcc matrix. A continuous film of A112MO formed in the surface modified region when aluminum was annealed after implantation with maximum molybdenum concentrations in the approximate range of 8-11 at.%. The microstructure of the A112Mo film was found to depend on the annealing temperature. A granular film formed after annealing at 550°C whereas a mottled film formed after annealing at 400°C. Sequential annealing experiments revealed that the mottled film transforms to a granular film which indicates the mottled film is metastable.

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