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

Molecular Dynamics Study on Interaction between Voids for Pure Aluminum

2010 ◽  
Vol 452-453 ◽  
pp. 845-848
Author(s):  
Shu Sheng Xu ◽  
Xiang Guo Zeng ◽  
Hua Yan Chen
Keyword(s):  
Molecular Dynamics ◽  
Pure Aluminum ◽  
Critical Distance ◽  
Atomic Scale ◽  
Embedded Atom Method ◽  
Face Centered Cubic ◽  
Embedded Atom ◽  
Modified Embedded Atom Method ◽  
Face Centered ◽  
The Impact

The voids in pure Aluminum always exit in the manufacturing process. The Modified Embedded Atom Method (MEAM) potential is employed in the molecular dynamics (MD) simulation at atomic scale to investigate the interaction between voids under the impact loading for pure Aluminum. The distance between the voids distributed along the loading orientation affects the failure mechanism seriously. The results show that there are 3 kinds of mechanisms with the change of the distance between voids: 1) coalescence takes place within a critical distance between voids under extra loading, 2) when the distance between voids reaches a certain value, each void cracks at 4 locations along with the slide direction <110> of face-centered cubic (fcc), respectively, 3) a stress shield zone appears when the ligament between the voids is at the size between the cases mentioned above, which brings out the phenomena that each of the voids cracks only at 2 locations, and no crack appeared at the stress shield zone.

Analytic embedded atom method potentials for face-centered cubic metals

1998 ◽  
Vol 13 (7) ◽  
pp. 1919-1927 ◽  
Author(s):  
S. S. Pohlong ◽  
P. N. Ram
Keyword(s):  
Reasonable Agreement ◽  
Mean Square Displacement ◽  
Pair Potential ◽  
Embedded Atom Method ◽  
Face Centered Cubic ◽  
Embedded Atom ◽  
Phonon Spectra ◽  
Morse Form ◽  
Face Centered ◽  
Experimental Values

The universal form of embedding function suggested by Banerjea and Smith together with a pair-potential of the Morse form are used to obtain embedded atom method (EAM) potentials for fcc metals: Cu, Ag, Au, Ni, Pd, and Pt. The potential parameters are determined by fitting to the Cauchy pressure (C12 − C44)/2, shear constant GV = (C11 − C12 + 3C44)/5, and C44, the cohesive energy and the vacancy formation energy. The obtained parameters are utilized to calculate the unrelaxed divacancy binding energy and the unrelaxed surface energies of three low-index planes. The calculated quantities are in reasonable agreement with the experimental values except perhaps the divacancy energy in a few cases. In a further application, lattice dynamics of these metals are discussed using the present EAM potentials. On comparison with experimental phonons, the agreement is good for Cu, Ag, and Ni, while in the other three metals, Au, Pd, and Pt, the agreement is not so good. The phonon spectra are in reasonable agreement with the earlier calculations. The frequency spectrum and the mean square displacement of an atom in Cu are in agreement with the experiment and other calculated results.

scholarly journals Direct observation of crystallization and melting with colloids

2019 ◽  
Vol 116 (4) ◽  
pp. 1180-1184 ◽  
Author(s):  
Hyerim Hwang ◽  
David A. Weitz ◽  
Frans Spaepen
Keyword(s):  
Energy Difference ◽  
Face Centered Cubic ◽  
Limited Growth ◽  
Free Energy Difference ◽  
Precise Control ◽  
Early Computer ◽  
Face Centered ◽  
Jump Frequencies ◽  
Kinetics Of ◽  
Kinetics Of Crystal Growth

We study the kinetics of crystal growth and melting of two types of colloidal crystals: body-centered cubic (BCC) crystals and face-centered cubic (FCC) crystals. A dielectrophoretic “electric bottle” confines colloids, enabling precise control of the motion of the interface. We track the particle motion, and by introducing a structural order parameter, we measure the jump frequencies of particles to and from the crystal and determine from these the free-energy difference between the phases and the interface mobility. We find that the interface is rough in both BCC and FCC cases. Moreover, the jump frequencies correspond to those expected from the random walk of the particles, which translates to collision-limited growth in metallic systems. The mobility of the BCC interface is greater than that of the FCC interface. In addition, contrary to the prediction of some early computer simulations, we show that there is no significant asymmetry between the mobilities for crystallization and melting.

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.

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.

scholarly journals Magnetic Properties and Microstructure of FeCoNi(CuAl)0.8Snx (0 ≤ x ≤ 0.10) High-Entropy Alloys

Entropy ◽  
2018 ◽  
Vol 20 (11) ◽  
pp. 872 ◽  
Author(s):  
Zhong Li ◽  
Chenxu Wang ◽  
Linye Yu ◽  
Yong Gu ◽  
Minxiang Pan ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
High Entropy Alloys ◽  
Face Centered Cubic ◽  
High Tc ◽  
Soft Magnets ◽  
High Entropy ◽  
Face Centered ◽  
Fcc Phase ◽  
Bcc Phase ◽  
Curie Temperatures

The present work exhibits the effects of Sn addition on the magnetic properties and microstructure of FeCoNi(CuAl)0.8Snx (0 ≤ x ≤ 0.10) high-entropy alloys (HEAs). The results show all the samples consist of a mixed structure of face-centered-cubic (FCC) phase and body-centered-cubic (BCC) phase. The addition of Sn promotes the formation of BCC phase, and it also affects the shape of Cu-rich nano-precipitates in BCC matrix. It also shows that the Curie temperatures (Tc) of the FCC phase and the saturation magnetization (Ms) of the FeCoNi(CuAl)0.8Snx (0 ≤ x ≤ 0.10) HEAs increase greatly while the remanence (Br) decreases after the addition of Sn into FeCoNi(CuAl)0.8 HEA. The thermomagnetic curves indicate that the phases of the FeCoNi(CuAl)0.8Snx (0 ≤ x ≤ 0.10) HEAs will transform from FCC with low Tc to BCC phase with high Tc at temperature of 600–700 K. This work provides a new idea for FeCoNi(CuAl)0.8Snx (0 ≤ x ≤ 0.10) HEAs for their potential application as soft magnets to be used at high temperatures.

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