Molecular Dynamics Methods and Large-Scale Simulations of Amorphous Materials

Vashishta, Priya; Kalia, Rajiv K.; Nakano, Aiichiro; Li, Wei; Ebbsjö, Ingvar

doi:10.1007/978-94-015-8832-4_7

Cited by 36 publications

(29 citation statements)

References 79 publications

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“…In the case of silica, we have investigated the behavior of molten, crystalline and amorphous states and also of permanently densified amorphous SiO 2 . The MD results for pair-distribution functions, static structure factors, vibrational densities of states, bond-angle distributions, and elastic moduli in crystalline and amorphous SiO 2 are in good agreement with experimental results [24][25][26]. The interatomic potential for silicon carbide is validated by comparing the MD results with experimental measurements of lattice constant, cohesive energy, elastic moduli (C 11 , C 12 , C 44 ), bulk modulus, and the phonon density-of-states of crystalline β-SiC.…”

Section: Molecular-dynamics Simulationssupporting

confidence: 81%

Multiresolution algorithms for massively parallel molecular dynamics simulations of nanostructured materials

Kalia

Campbell

Chatterjee

et al. 2000

Computer Physics Communications

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Section: Molecular-dynamics Simulationssupporting

confidence: 81%

Multiresolution algorithms for massively parallel molecular dynamics simulations of nanostructured materials

Kalia

Campbell

Chatterjee

et al. 2000

Computer Physics Communications

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“…The model devel-oped by Nakano et al has been successfully employed to describe the bulk and the surface of disordered phases of SiO 2 , viz. amorphous and porous silica, 10,13,[36][37][38][39][40][41] which are evidently relevant to the present problem. In this model, silicon is assumed to be coordinated to four oxygen atoms, that is, the network is chemically ordered.…”

Section: Computational Detailsmentioning

confidence: 86%

Structural properties of silicon dioxide thin films densified by medium-energy particles

et al. 2001

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Classical molecular-dynamics simulations have been carried out to investigate densification mechanisms in silicon dioxide thin films deposited on an amorphous silica surface, according to a simplified ion-beam assisted deposition (IBAD) scenario. We compare the structures resulting from the deposition of near-thermal (1 eV) SiO2 particles to those obtained with increasing fraction of 30 eV SiO2 particles. Our results show that there is an energy interval -between 12 and 15 eV per condensing SiO2 unit on average -for which the growth leads to a dense, low-stress amorphous structure, in satisfactory agreement with the results of low-energy ion-beam experiments. We also find that the crossover between low-and high-density films is associated with a tensile to compressive stress transition, and a simultaneous healing of structural defects of the a-SiO2 network, namely threeand four-fold rings. It is observed, finally, that densification proceeds through significant changes at intermediate length scales (4-10Å), leaving essentially unchanged the "building blocks" of the network, viz. the Si(O 1/2 )4 tetrahedra. This latter result is in qualitative agreement with the mechanism proposed to explain the irreversible densification of amorphous silica recovered from high pressures (∼ 15-20 GPa).

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“…Bulk Si 3 N 4 is modeled using a combination of two-and three-body interactions which include charge transfer, electronic polarizability, and covalent bonding effects. 15 This potential provides a good description of the structural and mechanical properties and dynamical behavior 16 ͑static structure factor, bulk and Young's moduli, and phonon density of states͒ and fracture behavior of crystalline and amorphous Si 3 N 4 . 17 To describe the bonding across the Si/Si 3 N 4 interface, the interface atoms are treated differently from those in the bulk.…”

mentioning

confidence: 99%

Multimillion-atom molecular dynamics simulation of atomic level stresses in Si(111)/Si3N4(0001) nanopixels

Bachlechner

Omeltchenko

Nakano

et al. 1998

Applied Physics Letters

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Ten million atom multiresolution molecular-dynamics simulations are performed on parallel computers to determine atomic-level stress distributions in a 54 nm nanopixel on a 0.1 m silicon substrate. Effects of surfaces, edges, and lattice mismatch at the Si͑111͒/Si 3 N 4 ͑0001͒ interface on the stress distributions are investigated. Stresses are found to be highly inhomogeneous in the nanopixel. The top surface of silicon nitride has a compressive stress of ϩ3 GPa and the stress is tensile, Ϫ1 GPa, in silicon below the interface. © 1998 American Institute of Physics. ͓S0003-6951͑98͒00116-8͔Sub-100 nm pixel sizes pose special challenges in Si electronics. In this regime, the significance of spatial inhomogeneities in the dopant distribution to the device characteristics is being increasingly appreciated.1 Spatially nonuniform stresses induced by such nanoscale pixellation may have profound impact 2 -rapidly varying stresses at and near edges may lead to defect formation or even initiate a crack. Understanding the stress distribution is therefore essential in the design of nanoscale devices.On larger (Ͼ1 m) length scales, edge stresses in Si/SiO 2 and Si/Si 3 N 4 have been examined utilizing the framework of linear elasticity and finite-element ͑FE͒ simulations. 3,4 In nanoscale devices, however, the surface-tovolume ratio is so large that the influence of surfaces, edges, and corners on elastic properties become significant. In addition, chemical bonding at the Si/Si 3 N 4 interface introduces types of stresses not present in silicon or silicon nitride materials. These effects have to be included in constitutive relations to achieve realistic description of nanoscale devices in the FE approach. An alternative approach is to use molecular-dynamics ͑MD͒ simulations where surface and interface bonding effects are explicitly included at the atomistic level. With recent progress in parallel computer architectures, it has now become possible to carry out direct atomistic simulations for submicron structures with realistic descriptions of the materials involved. In particular, largescale MD simulations have proven to be useful in the study of dynamic fracture.5 MD simulations provide spatially resolved stress distributions on the length scales not accessible to experimental techniques, such as MicroRaman spectroscopy.6 Such numerical experiments can be used to establish the validity of constitutive relations used in FE simulations, in particular the treatment of surface/interface/ edge effects.In this letter, the results of a ten million atom moleculardynamics study of atomic stress distribution in a Si/Si/Si 3 N 4 nanopixel are reported. The simulations were performed on 128 processors of the 256-processor HP Exemplar at Caltech requiring a total of 180 h of computational time. We have considered a crystalline Si 3 N 4 film forming a coherent Si͑111͒/Si 3 N 4 ͑0001͒ interface 7 with the Si mesa. An interatomic potential model for the Si/Si 3 N 4 interface has been developed using the charge transfer values computed from...

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Molecular Dynamics Methods and Large-Scale Simulations of Amorphous Materials

Cited by 36 publications

References 79 publications

Multiresolution algorithms for massively parallel molecular dynamics simulations of nanostructured materials

Multiresolution algorithms for massively parallel molecular dynamics simulations of nanostructured materials

Structural properties of silicon dioxide thin films densified by medium-energy particles

Multimillion-atom molecular dynamics simulation of atomic level stresses in Si(111)/Si3N4(0001) nanopixels

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