scholarly journals Initial Stage of Consolidation of Silicon-Carbide Nanocrystals under Pressure: A Tight-Binding Molecular-Dynamics Study

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Kenji Tsuruta
Keyword(s):  
Molecular Dynamics ◽  
Silicon Carbide ◽  
Tight Binding ◽  
Expansion Method ◽  
Nanocrystalline Silicon ◽  
External Pressure ◽  
Fermi Operator ◽  
Initial Stage ◽  
Long Time ◽  
Nanocrystalline Silicon Carbide

Tight-binding molecular-dynamics (TBMDs) simulations are performed to study atomic and electronic structures during high-temperature consolidation processes of nanocrystalline silicon carbide under external pressure. We employ a linear-scaling method (the Fermi-operator expansion method) with a scalable parallel algorithm for efficient calculations of the long time-scale phenomena. The results show that microscopic processes of the consolidation depend strongly on initial orientations of the nanocrystals. It is observed that an orientational rearrangement of the nanocrystals initially misaligned is induced by an instantaneous shearing force between nanocrystals, whereas the aligned system undergoes densification without shearing. Analysis on an effective-charge distribution and an average bond-order distribution reveals electronic-structure evolutions during these processes.

Tight-Binding Molecular Dynamics of Ceramic Nanocrystals Using Pc-Based Parallel Machines

1999 ◽  
Vol 581 ◽  
Author(s):  
Kenji Tsuruta ◽  
Hiroo Totsuji ◽  
Chieko Totsuji
Keyword(s):  
Molecular Dynamics ◽  
Electronic Structures ◽  
Parallel Machines ◽  
Tight Binding ◽  
Expansion Method ◽  
Surface Structures ◽  
Electronic Density ◽  
Pc Cluster ◽  
Fermi Operator ◽  
Gap States

ABSTRACTEvolution of atomic and electronic structures of silicon-carbide (SiC) nanocrystals during sintering is investigated by a tight-binding molecular dynamics (TBMD) method. An O(N) algorithm (the Fermi-operator expansion method) is employed for calculating electronic contributions in the energy and forces. Simulations are performed on our eight-node parallel PC cluster. In a sintering simulation of aligned (no tilt or twist) SiC nanocrystals at T = 1000K, we find that a neck is formed promptly without formation of defects. Analyses of local electronic density-of-states (DOS) and effective charges reveal that unsaturated bonds exist only in grain surfaces accompanying the gap states. In the case of tilted (<122>) nanocrystals, surface structures formed before sintering affect significantly the grainboundary formation.

Parallel Tight-Binding Simulations of Nanophase Ceramics: Atomic and Electronic Transport at Grain Boundaries

2000 ◽  
Vol 653 ◽  
Author(s):  
Kenji Tsuruta ◽  
Hiroo Totsuji ◽  
Chieko Totsuji
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Electronic Transport ◽  
Parallel Machines ◽  
Tight Binding ◽  
Expansion Method ◽  
Nanocrystalline Silicon ◽  
Contact Angles ◽  
Neck Formation ◽  
Fermi Operator

AbstractWe report on tight-binding molecular dynamics (TBMD) of neck formation processes and atomistic and electronic diffusivity at grain boundaries of nanocrystalline silicon carbide. The TBMD simulations are based on an O(N) algorithm (the Fermi-operator expansion method) for calculating electronic contributions to energy and forces. The code has been fully parallelized on our PC-based parallel machines. The TBMD simulations of collision of SiC nanospheres show that the processes of neck formation depend strongly on contact angles between the two grains. Atomic diffusions are quite different in the necks formed with different angles. Also, the electronic transport property at grain boundary is investigated via a TB representation of an electronic diffusivity. A preliminary result on the diffusivity at a Σ=9 grain boundary of SiC indicates significant enhancement of electron mobility along the grain boundary.

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