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Browsing by Author Pham, Khac Hung

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  • 61.pdf.jpg
  • Article

  • Dynamics and mechanism diffusion in silica liquid: Insight from simulation

    • Authors: Nguyen, Thi Thanh Ha; Nguyen, Quang Bau; Pham, Khac Hung (2012)

  • In this paper, we numerically study the diffusion mechanism at atomic level in silica liquid via molecular dynamics simulation. The model consisting of 1998 particles and using the BKS potential has been constructed at the temperature from 2600 to 4500 K. Furthermore, we track the evolution of network units with x=4, 5 and 6 over different time. The simulation shows that the diffusivity depends strongly not only on the rate of the exchanging the coordinated oxygens, but also on the correlation effect. This effect is caused by the specific distribution of the exchanging coordinated oxygens (ECO) through the space which leads to spatially heterogeneous dynamics in the liquid. Analyzing ...
  • 72.pdf.jpg
  • Article

  • The Microstructure of Amorphous Iron Nanoparticle

    • Authors: Mai, Thi Lan; Nguyen, Van Hong; Nguyen, Thu Nhan; Pham, Khac Hung (2013)

  • We have investigated the microstructure of amorphous iron nanoparticle (NP) and its bulk counterpart using molecular dynamic simulation with an embedded atom method (EAM). The NP models have a spherical shape and surface thickness of 3.6±0.125 Å. The microstructure of NP surface and core is analyzed through the coordination number distribution, density profile and distribution of simplex radius. Furthermore, the surface roughness has been identified via the distribution of distance from surface atom to NP surface. It was found that the microstructure of NP core is quite different from that of NP surface. However, their microstructure is almost independent on NP size. The simulation re...
  • 92.pdf.jpg
  • Article

  • Role of energetic disorder on diffusion in one-dimensional systems

    • Authors: Trinh, Van Mung; Pham, Khac Hung (2011)

  • The simulation of dynamical process of target particles in one-dimensional lattice is carried out for two types of energetic disorders. The particles are non-interacting except that ttre double occupancy is forbidden. It is found that the diffusion quantities such as the correlation factor and averaged time between two subsequent jumps are quite different for the lattices of site and transition disorders. However, the diffusion constant of both lattices is close to each other. Closed value of diffusion constant is obtained for the lattice with random distributed barriers. At the wide temperahue range the diffusivity follows the Arrhenius law. The blocking effect decreases the correla...
  • 85.pdf.jpg
  • Article

  • Simulation of Diffusion Mechanism and Dynamics in Alumina Liquid under Pressure

    • Authors: Nguyen, Thi Thanh Ha; Pham, Khac Hung (2013)

  • Diffusion mechanism and dynamics in Al2O3 liquidhave been studied via molecular dynamics simulation. Six models with different density and at temperature of 3000 K have been used to study the atomistic mechanism governing the process of the bond-breaking and bond-reformation (the transition AlOx®AlOx+1 and AlOx®AlOx-1). Calculation shows that the diffusion of particle Al is realized via the transition AlOx®AlOx±1 and the rate of transition AlOx®AlOx±1 monotonously increases with pressure. When applying pressure to liquid the diffusion mechanism changes from strong localization of transitions SiOx®SiOx±1 in the sample at ambient pressure to uniform distribution transitions SiOx®SiOx±1...
  • TL1.pdf.jpg
  • Article

  • Simulation of Diffusion Mechanism and Heterogeneous Dynamics in Network-forming Liquid

    • Authors: Nguyen, Thi Thanh Ha; Nguyen, Anh Dung; Nguyen, Quang Bau; Pham, Khac Hung (2016)

  • We have studied the diffusion mechanism in network-forming liquids via molecular dynamics simulation. Two models of silica liquid at temperatures of 2600 and 3500 K have been constructed. The motion of atoms is analyzed through reactions SiOx®SiOx±1, OSiy®OSiy±1 and coordination cells. It was shown that the reactions happen not randomly in the space, but they occur more frequently with some coordination cells and bonds Si-O. This effect enhances upon lowering the temperature. The number of reactions happening in the coordination cells is strongly correlated with the mobility of CC atom. We found that there are large rigid clusters which compose of immobile atoms and exist for long tim...
  • 115.pdf.jpg
  • Article

  • Simulation study of microscopic bubbles in amorphous alloy Co81.5B18.5

    • Authors: Pham, Huu Kien; Pham, Khac Hung; Vu, Van Hung (2010)

  • Simulation of the diffirsion mechanism via microscopic bubbles in amorphous materials is carried out using the statistical relaxation models Cos.5Bft.5 containing 2 x 105 atoms. The present work is focused on the role of these bubbles for self-diffirsion in amorphous solids. It was found that the numbers'of the vacancy bubbles in amorphous Cog1."B1g ,b vary from 1.4 x 10-3 to 4 x 10-3 per atom depending on the relaxation degree. The simulation shows the collective character of the atomic movement upon diffirsion atoms moving. Due to the large size in comparison with B atom, the jump of a Co diffirses atom leads to a significant local rearrangement of the atoms located near the VB. Mea...

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Browsing by Author Pham, Khac Hung

Jump to: 0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
or enter first few letters:  
Showing results 1 to 6 of 6
  • 61.pdf.jpg
  • Article

  • Dynamics and mechanism diffusion in silica liquid: Insight from simulation

    • Authors: Nguyen, Thi Thanh Ha; Nguyen, Quang Bau; Pham, Khac Hung (2012)

  • In this paper, we numerically study the diffusion mechanism at atomic level in silica liquid via molecular dynamics simulation. The model consisting of 1998 particles and using the BKS potential has been constructed at the temperature from 2600 to 4500 K. Furthermore, we track the evolution of network units with x=4, 5 and 6 over different time. The simulation shows that the diffusivity depends strongly not only on the rate of the exchanging the coordinated oxygens, but also on the correlation effect. This effect is caused by the specific distribution of the exchanging coordinated oxygens (ECO) through the space which leads to spatially heterogeneous dynamics in the liquid. Analyzing ...
  • 72.pdf.jpg
  • Article

  • The Microstructure of Amorphous Iron Nanoparticle

    • Authors: Mai, Thi Lan; Nguyen, Van Hong; Nguyen, Thu Nhan; Pham, Khac Hung (2013)

  • We have investigated the microstructure of amorphous iron nanoparticle (NP) and its bulk counterpart using molecular dynamic simulation with an embedded atom method (EAM). The NP models have a spherical shape and surface thickness of 3.6±0.125 Å. The microstructure of NP surface and core is analyzed through the coordination number distribution, density profile and distribution of simplex radius. Furthermore, the surface roughness has been identified via the distribution of distance from surface atom to NP surface. It was found that the microstructure of NP core is quite different from that of NP surface. However, their microstructure is almost independent on NP size. The simulation re...
  • 92.pdf.jpg
  • Article

  • Role of energetic disorder on diffusion in one-dimensional systems

    • Authors: Trinh, Van Mung; Pham, Khac Hung (2011)

  • The simulation of dynamical process of target particles in one-dimensional lattice is carried out for two types of energetic disorders. The particles are non-interacting except that ttre double occupancy is forbidden. It is found that the diffusion quantities such as the correlation factor and averaged time between two subsequent jumps are quite different for the lattices of site and transition disorders. However, the diffusion constant of both lattices is close to each other. Closed value of diffusion constant is obtained for the lattice with random distributed barriers. At the wide temperahue range the diffusivity follows the Arrhenius law. The blocking effect decreases the correla...
  • 85.pdf.jpg
  • Article

  • Simulation of Diffusion Mechanism and Dynamics in Alumina Liquid under Pressure

    • Authors: Nguyen, Thi Thanh Ha; Pham, Khac Hung (2013)

  • Diffusion mechanism and dynamics in Al2O3 liquidhave been studied via molecular dynamics simulation. Six models with different density and at temperature of 3000 K have been used to study the atomistic mechanism governing the process of the bond-breaking and bond-reformation (the transition AlOx®AlOx+1 and AlOx®AlOx-1). Calculation shows that the diffusion of particle Al is realized via the transition AlOx®AlOx±1 and the rate of transition AlOx®AlOx±1 monotonously increases with pressure. When applying pressure to liquid the diffusion mechanism changes from strong localization of transitions SiOx®SiOx±1 in the sample at ambient pressure to uniform distribution transitions SiOx®SiOx±1...
  • TL1.pdf.jpg
  • Article

  • Simulation of Diffusion Mechanism and Heterogeneous Dynamics in Network-forming Liquid

    • Authors: Nguyen, Thi Thanh Ha; Nguyen, Anh Dung; Nguyen, Quang Bau; Pham, Khac Hung (2016)

  • We have studied the diffusion mechanism in network-forming liquids via molecular dynamics simulation. Two models of silica liquid at temperatures of 2600 and 3500 K have been constructed. The motion of atoms is analyzed through reactions SiOx®SiOx±1, OSiy®OSiy±1 and coordination cells. It was shown that the reactions happen not randomly in the space, but they occur more frequently with some coordination cells and bonds Si-O. This effect enhances upon lowering the temperature. The number of reactions happening in the coordination cells is strongly correlated with the mobility of CC atom. We found that there are large rigid clusters which compose of immobile atoms and exist for long tim...
  • 115.pdf.jpg
  • Article

  • Simulation study of microscopic bubbles in amorphous alloy Co81.5B18.5

    • Authors: Pham, Huu Kien; Pham, Khac Hung; Vu, Van Hung (2010)

  • Simulation of the diffirsion mechanism via microscopic bubbles in amorphous materials is carried out using the statistical relaxation models Cos.5Bft.5 containing 2 x 105 atoms. The present work is focused on the role of these bubbles for self-diffirsion in amorphous solids. It was found that the numbers'of the vacancy bubbles in amorphous Cog1."B1g ,b vary from 1.4 x 10-3 to 4 x 10-3 per atom depending on the relaxation degree. The simulation shows the collective character of the atomic movement upon diffirsion atoms moving. Due to the large size in comparison with B atom, the jump of a Co diffirses atom leads to a significant local rearrangement of the atoms located near the VB. Mea...