Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

Amorphous alloys were first developed over 40 years ago and found applications as magnetic core or reinforcement added to other materials. The scope of applications is limited due to the small thickness in the region of only tens of microns. The research effort in the past two decades, mainly pioneered by a Japanese- and a US-group of scientists, has substantially relaxed this size constrain. Some bulk metallic glasses can have tensile strength up to 3000 MPa with good corrosion resistance, reasonable toughness, low internal friction and good processability. Bulk metallic glasses are now being used in consumer electronic industries, sporting goods industries, etc. In this paper, the authors reviewed the recent development of new alloy systems of bulk metallic glasses. The properties and processing technologies relevant to the industrial applications of these alloys are also discussed here. The behaviors of bulk metallic glasses under extreme conditions such as high pressure and low temperature are especially addressed in this review. In order that the scope of applications can be broadened, the understanding of the glass-forming criteria is important for the design of new alloy systems and also the processing techniques.

https://www.tcd.ie/Physics/people/Graham.Cross/SF%20Poster%202011/Shek-MaterSciEng04-Bulk%20Metallic%20Glasses.pdf

Bulk metallic glasses

Nitrogen doping has been an effective way to tailor the properties of graphene and render its potential use for various applications. Three common bonding configurations are normally obtained when doping nitrogen into the graphene: pyridinic N, pyrrolic N, and graphitic N. This paper reviews nitrogen-doped graphene, including various synthesis methods to introduce N doping and various characterization techniques for the examination of various N bonding configurations. Potential applications of N-graphene are also reviewed on the basis of experimental and theoretical studies.

https://s3-eu-west-1.amazonaws.com/pfigshare-u-files/1431849/NitrogenReviewonRecentProgressinNitrogenDopedGrapheneSynthesisCharacterizationandItsPotentialApplications.pdf

Review on Recent Progress in Nitrogen-Doped Graphene: Synthesis, Characterization, and Its Potential Applications

https://www.tcd.ie/Physics/people/Graham.Cross/SF%20Poster%202011/Schuh-ActaMater07-Mechanical%20behaviour%20of%20amorphous%20alloys.pdf

Mechanical behavior of amorphous alloys

/pdf/molecular-evolutionary-genetics-analysis-1uvpbl4lte.pdf

Molecular Evolutionary Genetics Analysis

In this communication, we successfully synthesized a new SnO(2) nanoarchitecture: extremely thin sheets, with minimum thicknesses of 1.5-3.0 nm. The products were prepared through a facile hydrothermal treatment using tin dichloride as the precursor. Planar or scrolled SnO(2) sheets were carefully examined by transmission electron microscopy. The assemblies of these sheets have a high BET surface area of 180.3 m(2)/g and extraordinarily large pore volume of 1.028 cm(3)/g. They also exhibit a high lithium storage capacity and excellent cyclability due to its nanometer-sized frame and breathable characteristic.

Large-Scale Synthesis of SnO2 Nanosheets with High Lithium Storage Capacity

Ferromagnetic zinc ferrite nanocrystals at ambient temperature were synthesized via the thermal decomposition of metal−surfactant complexes. Characterization measurements including transmission electron microscopy and X-ray diffraction were performed for as-synthesized ZnFe2O4 particles. The sample has a relatively narrow size distribution with an average particle size of 9.8 ± 0.2 nm and standard deviation of 30%. The as-synthesized zinc ferrite nanocrystals are superparamagnetic at room temperature with a blocking temperature TB = 68 ± 2 K and a saturation magnetization MS = 65.4 emu·g-1 at T = 10 K, which are caused by the change in the inversion degree of the spinel structure. A coercive field of HC = 102 ± 5 Oe in the blocked state indicates small particle anisotropy, although evidence of surface spin canting was inferred from magnetization data in the as-synthesized ZnFe2O4 nanocrystals. Our results demonstrate that magnetic properties of magnetic particles can be largely modified by just changing p...

http://www.unizar.es/gfgoya/index_archivos/PDF/JPCC2007_ZnFe2O4.pdf

ZnFe2O4 Nanocrystals: Synthesis and Magnetic Properties

Zr–(Cu,Ag)–Al bulk metallic glasses

Geometries, electronic structures, and magnetic properties of transition metal $M$ adatom and dimer adsorbed graphene have been studied ($M=\text{Fe}$, Co, Ni, and Cu). With adatom adsorption, we confirm the previously reported stable adsorption site, and the adatoms are chemically bonded with graphene except the copper adatom. With dimer adsorption, we observed that the stable configurations are dependent on the exchange-correlation functional for the iron dimer and nickel dimer; while the stable configurations do not depend on the functional for the cobalt and copper dimer. The adsorption energy indicates the copper dimer can barrierlessly diffuse along the graphene C-C bonds. With iron or cobalt adatom adsorption, graphene becomes a half-metal which can be used as a spin-filtering material. The iron dimer adsorbed graphene is also a half-metal, but the cobalt dimer adsorbed graphene is not. Both local-density approximation and generalized gradient approximation yield consistent results for the nickel adatom adsorbed graphene, which is the system is semiconducting and nonmagnetic due to the strong binding between nickel and graphene. However, different exchange-correlation functionals lead to controversial results for the magnetic and transport properties of nickel dimer adsorbed graphene. The copper adatom adsorbed on graphene exhibits $1{\ensuremath{\mu}}_{B}$ local magnetic moment, but the dimer does not show any magnetism. These results show that graphene properties can be effectively modulated by transition metal adsorption and that the transition metal adsorbed graphene can serve as potential materials in nanoelectronics, spintronics, or electrochemistry.

Transition metal adatom and dimer adsorbed on graphene: Induced magnetization and electronic structures

First-principles calculations are performed to study the geometry, electronic structure and magnetic properties of light non-metallic atom-doped graphene (B, N, O and F). The planar structure and the quasi-linear energy dispersion near the Dirac point remain through doping with B and N atoms, by which p-type doping and n-type doping graphene are respectively induced. A bandgap of about 0.5 eV is generated through O doping, and geometrically the O atom is also in the graphene plane. No magnetic moment is detected in B- , N- and O-doped graphene. For F doping, the F atom bonds with one of the carbon atoms close to the vacancy, with the other two carbon atoms undergoing a Jahn-Teller distortion. A weak polarized magnetic moment of 0.71 µ(B) is detected through F doping.

https://iopscience.iop.org/article/10.1088/0957-4484/21/50/505202/pdf

Jianzhong Jiang

Papers

Large-Scale Synthesis of SnO2 Nanosheets with High Lithium Storage Capacity

ZnFe2O4 Nanocrystals: Synthesis and Magnetic Properties

Zr–(Cu,Ag)–Al bulk metallic glasses

Transition metal adatom and dimer adsorbed on graphene: Induced magnetization and electronic structures

Light non-metallic atom (B, N, O and F)-doped graphene: a first-principles study