There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Additive manufacturing of metallic components – Process, structure and properties

Principles of equal-channel angular pressing as a processing tool for grain refinement

A molecular dynamics study of the mechanical properties of hydrogen functionalized graphene

Graphyne is the allotrope of graphene. In this letter, four different graphynes (α, β, γ, and 6,6,12-graphenes) are investigated by molecular dynamics simulations to explore their mechanical properties and failure mechanisms. It is found that the presence of the acetylenic linkages in graphynes leads to a significant reduction in fracture stress and Young’s modulus with the degree of reduction being proportional to the percentage of the linkages. This deterioration in mechanical properties stems from the low atom density in graphynes and weak single bonds in the acetylenic linkages where the facture is initiated.

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Mechanical properties of graphynes under tension: A molecular dynamics study

We investigated the thermal conduction of monolayer MoS2 sheet and nanoribbons using molecular dynamics simulations. Room temperature thermal conductivity of monolayer MoS2 is found to be 1.35 W/mK, which is three orders of magnitude lower than that of graphene. In contrast to the remarkable size effect observed in graphene nanoribbons, the thermal conductivity of MoS2 nanoribbons is insensitive to width (3–16 nm), length (4–111 nm), and the type of edge, which are explained by the local heat flux analysis and phonon scattering mechanisms. The low thermal conductivity together with reported high Seebeck coefficient opens up the possibility to realize MoS2-based two-dimensional thermoelectric devices.

Phonon thermal conductivity of monolayer MoS2 sheet and nanoribbons

A theoretical analysis of the thermal conductivity of hydrogenated graphene

As a new two-dimensional (2D) material, phosphorene has drawn growing attention owing to its novel electronic properties, such as layer-dependent direct bandgaps and high carrier mobility. Herein we investigate the in-plane and cross-plane thermal conductivities of single- and multi-layer phosphorene, focusing on geometrical (sample size, orientation and layer number) and strain (compression and tension) effects. A strong anisotropy is found in the in-plane thermal conductivity with its value along the zigzag direction being much higher than that along the armchair direction. Interestingly, the in-plane thermal conductivity of multi-layer phosphorene is insensitive to the layer number, which is in strong contrast to that of graphene where the interlayer interactions strongly influence the thermal transport. Surprisingly, tensile strain leads to an anomalous increase in the in-plane thermal conductivity of phosphorene, in particular in the armchair direction. Both the in-plane and cross-plane thermal conductivities can be modulated by external strain; however, the strain modulation along the cross-plane direction is more effective and thus more tunable than that along the in-plane direction. Our findings here are of great importance for the thermal management in phosphorene-based nanoelectronic devices and for thermoelectric applications of phosphorene.

Qing-Xiang Pei

Papers

A molecular dynamics study of the mechanical properties of hydrogen functionalized graphene

Mechanical properties of graphynes under tension: A molecular dynamics study

Phonon thermal conductivity of monolayer MoS2 sheet and nanoribbons

A theoretical analysis of the thermal conductivity of hydrogenated graphene

Thermal conductivities of single- and multi-layer phosphorene: a molecular dynamics study