Structural and dynamics properties of double icosahedral Pd-Ag-Pt trimetallic clusters

2020 ◽  
Vol 34 (08) ◽  
pp. 2050063
Author(s):  
Ali Kemal Garip ◽  
Songül Taran
Keyword(s):  
Monte Carlo ◽  
Systematic Investigation ◽  
Chemical Ordering ◽  
Basin Hopping ◽  
Gupta Potential

Using Monte Carlo Basin-hopping algorithm within the Gupta potential, a systematic investigation has been performed for the best chemical ordering structures of 19-atom trimetallic [Formula: see text] nanoclusters with double icosahedral geometry. The structures with the lowest energy at Gupta level are then re-optimized by DFT relaxations and the DFT relaxations confirmed the lowest energy structures obtained at the Gupta level indicating the double icosahedron structure is favorable for 19-atom [Formula: see text] nanoclusters. It was observed that the caloric curves exhibit a smoother transition with structural isomerizations other than a sharp jump behavior.

GLOBAL MINIMA FOR PdN (N = 5–80) CLUSTERS DESCRIBED BY SUTTON–CHEN POTENTIAL

2007 ◽  
Vol 18 (08) ◽  
pp. 1351-1359 ◽  
Author(s):  
HAYDAR ARSLAN
Keyword(s):  
Monte Carlo ◽  
Energy Surface ◽  
Central Atom ◽  
Low Energy ◽  
Global Minima ◽  
Many Body ◽  
Pd Clusters ◽  
Body Potential ◽  
Basin Hopping ◽  
Theoretical Results

The structure and energetics of Pd N (N = 5–80) clusters have been studied extensively by a Monte Carlo method based on Sutton–Chen many-body potential. The basin-hopping algorithm is used to find the low-energy minima on the potential energy surface for each nuclearity. A variety of structure types (icosahedral, decahedral and fcc closed-packed) are observed for Pd clusters. Some of the icosahedral global minima do not have a central atom. The resulting structures have been compared with the previous theoretical results.

Investigation of the chemical ordering and thermal properties of the Rh–Ag–Au nanoalloys

2021 ◽  
Author(s):  
Huseyin Yildirim
Keyword(s):  
Md Simulation ◽  
Energy Analysis ◽  
Surface Melting ◽  
Melting Temperatures ◽  
The Third ◽  
Chemical Ordering ◽  
Caloric Curve ◽  
The Difference ◽  
Two Stages ◽  
Gupta Potential

In this paper, the melting behaviors of Rh–Ag–Au nanoalloys are investigated with MD simulation. For Rh–Ag–Au nanoalloys, icosahedron structure was considered. The local optimizations of Rh–Ag–Au nanoalloys were carried out with the BH algorithm. The interatomic interactions were modeled with the Gupta potential. The local optimization results of Rh–Ag–Au nanoalloys show that Au and Ag atoms prefer to locate on the surface, and Rh atoms prefer to locate in the inner shells. The bond order parameter result is compatible with the excess energy analysis. It is noted that structures with more Ag–Au bonds are more energetically stable. Caloric curve, heat capacity, Lindemann index, and RMSD methods were used for estimating the melting temperatures of Rh–Ag–Au nanoalloys. According to the simulation results, melting temperatures depend on the composition. Also, it is discovered that nanoalloys are generally melting in two stages. Surface melting of the third shell is occupied by Ag and Au atoms, and then homogeneous melting of the inner shells is occupied by Rh atoms. It is found that the difference between surface melting temperatures and homogeneous melting temperatures in Ag-poor compositions is more significant than that of Ag-rich nanoalloys. In addition, the melting temperatures of the nanoalloys are found to be increased as the size of nanoalloys increases.

Aspects of Experimental Errors and Data Reduction Schemes From Spherical Indentation of Isotropic Materials

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
J. K. Phadikar ◽  
T. A. Bogetti ◽  
A. M. Karlsson
Keyword(s):  
Sensitivity Analysis ◽  
Experimental Investigation ◽  
Monte Carlo ◽  
Condition Number ◽  
Data Reduction ◽  
Material Properties ◽  
Analytical Method ◽  
Systematic Investigation ◽  
Spherical Indentation ◽  
Experimental Errors

Sensitivity to experimental errors determines the reliability and usefulness of any experimental investigation. Thus, it is important to understand how various test techniques are affected by expected experimental errors. Here, a semi-analytical method based on the concept of condition number is explored for systematic investigation of the sensitivity of spherical indentation to experimental errors. The method is employed to investigate the reliability of various possible spherical indentation protocols, providing a ranking of the selected data reduction protocols from least to most sensitive to experimental errors. Explicit Monte Carlo sensitivity analysis is employed to provide further insight of selected protocol, supporting the ranking. The results suggest that the proposed method for estimating the sensitivity to experimental errors is a useful tool. Moreover, in the case of spherical indentation, the experimental errors must be very small to give reliable material properties.

Atomic Ordering in Nano-layered FePt: Multiscale Monte Carlo Simulation

2009 ◽  
Vol 1177 ◽  
Author(s):  
Rafal Kozubski ◽  
Miroslaw Kozlowski ◽  
Jan Wrobel ◽  
Tomasz Wejrzanowski ◽  
Krzysztof J Kurzydlowski ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Free Surface ◽  
Antiphase Boundary ◽  
Thin Layers ◽  
Domain Growth ◽  
Magnetic Storage ◽  
Easy Magnetization ◽  
Chemical Ordering ◽  
Ordering Kinetics ◽  
Magnetic Storage Media

AbstractCombined nano- and mesoscale simulation of chemical ordering kinetics in nano-layered L10 AB binary system was performed. In the nano- (atomistic) scale Monte Carlo (MC) technique with vacancy mechanism of atomic migration was implemented with diverse system models. The mesoscale microstructure evolution was, in turn, modeled by means of MC procedure simulating antiphase boundary (APB) motion as controlled by APB energies evaluated within the nano-scale simulations. The study addressed FePt thin layers considered as a material for ultra-high density magnetic storage media and revealed metastability of the L10 c-variant superstructure with monoatomic planes parallel to the (001) free surface and off-plane easy magnetization. The layers, initially perfectly ordered in the L10 c-variant, showed homogenous disordering running in parallel with a spontaneous re-orientation of the monoatomic planes into a mosaic-microstructure composed of L10 a- and b-variant domains with (100)- and (010)-type monoatomic planes, respectively. The domains nucleated heterogeneously on the Fe free surface of the layer, grew discontinuously inwards its volume and finally relaxed generating an equilibrium microstructure of the system. Two �atomistic-scale� processes: (i) homogenous disordering and (ii) nucleation of the L10 a- and b-variant domains showed characteristic time scales. The same was observed for the meso-scale processes: (i) heterogeneous L10 variant domain growth and (ii) domain microstructure relaxation. The above phenomena modelled within the present study by means of multiscale MC simulations have recently been observed experimentally in epitaxially deposited thin films of FePt.

scholarly journals Structural optimization of Fen-Ptm (5 n+m 24) alloy clusters based on an improved Basin-Hopping Monte Carlo algorithm

2017 ◽  
Vol 66 (5) ◽  
pp. 053601
Author(s):  
Liu Tun-Dong ◽  
Li Ze-Peng ◽  
Ji Qing-Shuang ◽  
Shao Gui-Fang ◽  
Fan Tian-E ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Structural Optimization ◽  
Monte Carlo Algorithm ◽  
Basin Hopping ◽  
Alloy Clusters

Investigation of structural and energetic behavior of 55-atom Pt–Ag–Au ternary nanoalloys

2021 ◽  
pp. 2150174
Author(s):  
Hüseyin Yıldırım ◽  
Ali Kemal Garip
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Energy Analysis ◽  
Many Body ◽  
Functional Theory ◽  
Mixing Energy ◽  
Chemical Ordering ◽  
The One ◽  
Body Potential ◽  
Basin Hopping

A systematic theoretical investigation of structural and energetic behaviors of 55-atom Pt–Ag–Au ternary nanoalloys has been performed in two different composition systems. We have performed Gupta and Density Functional Theory (DFT) approaches on chosen systems. The Basin-Hopping algorithm is used for structural optimizations of PtnAg[Formula: see text]Au[Formula: see text] ([Formula: see text]–13) and PtnAu[Formula: see text]Ag[Formula: see text] ([Formula: see text]–13) ternary nanoalloys with Gupta many-body potential to model interatomic interactions. Local optimization results show that while the tendency of Au atoms to be located varies according to the composition system, the tendency of Pt and Ag atoms to be located does not change in both. For all compositions of Pt–Ag–Au nanoalloys, the structures with the best chemical ordering were then reoptimized by DFT relaxations and the mixing energies of the Gupta and DFT levels were compared. Our mixing energy analysis showed that PtnAg[Formula: see text]Au[Formula: see text] ([Formula: see text]–13) nanoalloys are not energetically suitable for mixing at both Gupta and DFT level. Also, mixing energy variations of PtnAu[Formula: see text]Ag[Formula: see text] ([Formula: see text]–13) nanoalloys obtained at Gupta level does not agree with the one obtained at DFT level. In addition, it has been found that the minimization energy changes when an atom in the central site is exchanging by an atom in the second shell and surface.

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