Stability and Structural Transition of Gold Nanowires under Their Own Surface Stresses

2004 ◽  
Vol 854 ◽  
Author(s):  
Ken Gall ◽  
Michael Haftel ◽  
Jiankuai Diao ◽  
Martin L. Dunn ◽  
Noam Bernstein ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Tight Binding ◽  
Gold Nanowires ◽  
Face Centered Cubic ◽  
First Principle ◽  
Local Energy Minimum ◽  
Surface Stresses ◽  
Embedded Atom ◽  
Theoretical Approaches ◽  
Face Centered

ABSTRACTFirst-principle, tight binding, and semi-empirical embedded atom calculations are used to investigate a tetragonal phase transformation in gold nanowires. As wire diameter is decreased, tight binding and modified embedded atom simulations predict a surface-stress-induced phase transformation from a face-centered-cubic (fcc) <100> nanowire into a body-centered-tetragonal (bct) nanowire. In bulk gold, all theoretical approaches predict a local energy minimum at the bct phase, but tight binding and first principle calculations predict elastic instability of the bulk bct phase. The predicted existence of the stable bct phase in the nanowires is thus attributed to constraint from surface stresses. The results demonstrate that surface stresses are theoretically capable of inducing phase transformation and subsequent phase stability in nanometer scale metallic wires under appropriate conditions.

Tetragonal Phase Transformation in Gold Nanowires

2004 ◽  
Vol 127 (4) ◽  
pp. 417-422 ◽  
Author(s):  
Ken Gall ◽  
Jiankuai Diao ◽  
Martin L. Dunn ◽  
Michael Haftel ◽  
Noam Bernstein ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Tetragonal Phase ◽  
Tight Binding ◽  
Gold Nanowires ◽  
Face Centered Cubic ◽  
First Principle ◽  
Local Energy Minimum ◽  
Surface Stresses ◽  
Embedded Atom ◽  
Theoretical Approaches

First principle, tight binding, and semi-empirical embedded atom calculations are used to investigate a tetragonal phase transformation in gold nanowires. As wire diameter is decreased, tight binding and modified embedded atom simulations predict a surface-stress-induced phase transformation from a face-centered-cubic (fcc) ⟨100⟩ nanowire into a body-centered-tetragonal (bct) nanowire. In bulk gold, all theoretical approaches predict a local energy minimum at the bct phase, but tight binding and first principle calculations predict elastic instability of the bulk bct phase. The predicted existence of the stable bct phase in the nanowires is thus attributed to constraint from surface stresses. The results demonstrate that surface stresses are theoretically capable of inducing phase transformation and subsequent phase stability in nanometer scale metallic wires under appropriate conditions.

Simulation of Void Growth at High Strain-Rate

1998 ◽  
Vol 539 ◽  
Author(s):  
J. Belak ◽  
R. Minich
Keyword(s):  
Molecular Dynamics ◽  
Perfect Crystal ◽  
Dislocation Nucleation ◽  
Growth Exponent ◽  
Face Centered Cubic ◽  
Dynamics Modeling ◽  
Cubic Metals ◽  
Embedded Atom ◽  
Molecular Dynamics Modeling ◽  
Face Centered

AbstractThe dynamic fracture (spallation) of ductile metals is known to initiate through the nucleation and growth of microscopic voids. Here, we apply atomistic molecular dynamics modeling to the early growth of nanoscale (2nm radius) voids in face centered cubic metals using embedded atom potential models. The voids grow through anisotropic dislocation nucleation and emission into a cuboidal shape in agreement with experiment. The mechanism of this nucleation process is presented. The resulting viscous growth exponent at late times is about three times larger than expected from experiment for microscale voids, suggesting either a length scale dependence or a inadequacy of the molecular dynamics model such as the perfect crystal surrounding the void.

Molecular Dynamics Simulation of the Solidification of Liquid Nickel Nanowires

2007 ◽  
Vol 121-123 ◽  
pp. 1053-1056
Author(s):  
Guo Rong Zhong ◽  
Qiu Ming Gao
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Dynamics Simulation ◽  
Face Centered Cubic ◽  
Liquid Nickel ◽  
Cooling Rates ◽  
Final Structure ◽  
Embedded Atom ◽  
Nickel Nanowires ◽  
Face Centered

Molecular dynamics simulation of the solidification behavior of liquid nickel nanowires has been carried out based on the embedded atom potential with different cooling rates. The nanowires constructed with a face-centered cubic structure and a one-dimensional (1D) periodical boundary condition along the wire axis direction. It is found that the final structure of Ni nanowires strongly depend on the cooling rates during solidification from liquid. With decreasing cooling rates the final structure of the nanowires varies from amorphous to crystalline via helical multi-shelled structure.

Mechanical stability and strength of a single Au crystal

2008 ◽  
Vol 86 (7) ◽  
pp. 935-941 ◽  
Author(s):  
J -M Zhang ◽  
Y Yang ◽  
K -W Xu ◽  
V Ji
Keyword(s):  
Mechanical Stability ◽  
Energy Difference ◽  
Theoretical Strength ◽  
Stable Region ◽  
Embedded Atom Method ◽  
Face Centered Cubic ◽  
Embedded Atom ◽  
Free Body ◽  
Face Centered ◽  
Bcc Phase

The structural stability and theoretical strength of a Au face-centered cubic (FCC) crystal under uniaxial loading is investigated by combining the modified analytical embedded atom method (MAEAM) with Born stability criteria. The results show that under sufficient compression, there exists a stress-free body-centered cubic (BCC) phase, which is unstable and slips spontaneously to a stress-free metastable body-centered tetragonal phase by consuming internal energy. The structural energy difference between the BCC and FCC phases is in good agreement with the experimental value. The stable region ranged from –2.21 GPa to 6.31 GPa in the theoretical strength or from –9.83% to 7.87% in the strain correspondingly.PACS Nos.: 62.20.–x, 61.50.Ks, 81.05.Bx

INFLUENCE OF PRESSURE AND ATOMIC CONCENTRATION ON STRUCTURE AND MECHANICAL PROPERTIES OF CuNi ALLOY BY MOLECULAR DYNAMICS SIMULATION

2020 ◽  
Vol 65 (6) ◽  
pp. 54-60
Author(s):  
Thao Nguyen Thi ◽  
Hang Trinh Thi Thu
Keyword(s):  
Mechanical Properties ◽  
Dynamics Simulation ◽  
Embedded Atom Method ◽  
Face Centered Cubic ◽  
Atomic Concentration ◽  
Common Neighbor ◽  
Hexagonal Close Packed ◽  
Embedded Atom ◽  
The Common ◽  
Face Centered

The structure and mechanical properties of Cu80Ni20 and Cu50Ni50 alloys with the size of 4000 atoms have been investigated using molecular dynamic (MD) simulation. The interactions between atoms of the system were calculated by the Sutton-Chen type of embedded atom method. Using a cooling rate of 0.01 K\ps, we find that both Ni and Cu atoms are crystallized into face centered cubic (fcc) and the hexagonal close packed (hcp) phases when the sample was cooled down to 300 K. The atomic concentration of CuNi alloy samples have a different effect on this crystallization. The transformation to the crystalline phase is analyzed through the Common Neighbor Analysis (CNA) methods. Furthermore, we focus on the dependence of the mechanical properties of CuNi alloy on pressure and atomic concentration

57Fe Mössbauer isomer shifts in random face-centered cubic Fe–Ni alloys: Experiment versus electronic structure calculations

1992 ◽  
Vol 70 (12) ◽  
pp. 1241-1243 ◽  
Author(s):  
D. G. Rancourt ◽  
J. Y. Ping ◽  
M.-Z. Dang
Keyword(s):  
Tight Binding ◽  
Stability Limit ◽  
Quantitative Agreement ◽  
Face Centered Cubic ◽  
Linear Variation ◽  
Ni Alloys ◽  
Volume Dependence ◽  
Experiment Versus ◽  
Face Centered ◽  
Structure Calculations

Measured 57Fe-isomer shifts for face-centered cubic FeyNi1−y alloys show a linear variation with ∂1S/∂y = +0.10 mm s−1 up to [Formula: see text] followed by a plateau at [Formula: see text], up to the structural stability limit at [Formula: see text]. This is in disagreement with recent ab initio calculations, however, the increase at [Formula: see text] is in quantitative agreement with an older modified tight-binding approach in which the increase arises from an atomic volume dependence. The plateau is an anomaly that sets in at the same composition as that at which the saturation moments start to deviate from the Slater–Pauling curve.

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.

In Situ HREM Observation of Phase Transformation Process in FePt and FePtCu Nanoparticles

2005 ◽  
Vol 907 ◽  
Author(s):  
Masatoshi Nakanishi ◽  
Gen-ichi Furusawa ◽  
Kokichi Waki ◽  
Yasushi Hattori ◽  
Takeo Kamino ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Single Crystal ◽  
Particle Formation ◽  
Cubic Phase ◽  
Fept Nanoparticles ◽  
Crystal Formation ◽  
Face Centered Cubic ◽  
Shaped Particle ◽  
Face Centered

AbstractThe processes of phase transformation in individual nanoparticles of FePt and FePtCu synthesized by the reverse micelle method, which are chemically homogeneous and monodisperse, have been investigated by an in-situ HREM observation in a FE-TEM. Polycrystalline FePt particles, initially of chemically disordered face-centered cubic phase (A1) were reconstructed into A1 single crystals between 25 °C and 650 °C, followed by phase transformation from A1 to chemically ordered face-centered tetragonal phase (L10) which began between 650 °C and 680 °C. The coalescence began concurrently with phase transformation, i. e., between 650 °C and 680 °C. They turned to be a round-shaped L10 particle between 680 °C and 720 °C. The single crystal formation, the phase transformation from A1 to L10, the coalescence and the round-shaped particle formation were also observed in the FePtCu nanoparticles. The temperatures of single crystal formation, phase transformation (and coalescence) and round-shaped particle formation of the FePtCu nanoparticles were between 25 °C and 500 °C, between 550 °C and 600 °C and between 600 °C and 650 °C, respectively. These temperatures were substantially lower than those for the FePt nanoparticles.

Intergranular Strain and Phase Transformation in a Cobalt-Based Superalloy

2006 ◽  
Vol 524-525 ◽  
pp. 893-898 ◽  
Author(s):  
Michael L. Benson ◽  
A.D. Stoica ◽  
Peter K. Liaw ◽  
Hahn Choo ◽  
T.A. Saleh ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Strain Analysis ◽  
Face Centered Cubic ◽  
Macroscopic Stress ◽  
Intergranular Strain ◽  
Lattice Strains ◽  
The Face ◽  
Face Centered ◽  
Fcc Phase ◽  
In Situ Neutron Diffraction

ULTIMET® alloy, a cobalt-based superalloy with good corrosion and wear resistant properties, exhibits a deformation-induced phase transformation from the face-centered-cubic (FCC) phase to the hexagonal-close-packed (HCP) phase. The HCP phase formation during monotonic tensile loading was investigated using in-situ neutron diffraction. The HCP phase is first observed at a stress level of 810 MPa, which is well beyond macroscopic yielding. Strain analysis is performed on the FCC phase diffraction data in order to relate the lattice-strain development with the evolution of the new HCP phase. A method of calculating the effective macroscopic stress associated with the measured lattice strains is presented here. The effective stress can then be compared to the applied macroscopic stress in order to draw conclusions about the load-partitioning behavior of the material as a new phase develops.

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