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

Preface Acknowledgements Notation Part I. Overview and Background Topics: 1. Introduction 2. Overview 3. Theoretical background 4. Periodic solids and electron bands 5. Uniform electron gas and simple metals Part II. Density Functional Theory: 6. Density functional theory: foundations 7. The Kohn-Sham ansatz 8. Functionals for exchange and correlation 9. Solving the Kohn-Sham equations Part III. Important Preliminaries on Atoms: 10. Electronic structure of atoms 11. Pseudopotentials Part IV. Determination of Electronic Structure, The Three Basic Methods: 12. Plane waves and grids: basics 13. Plane waves and grids: full calculations 14. Localized orbitals: tight binding 15. Localized orbitals: full calculations 16. Augmented functions: APW, KKR, MTO 17. Augmented functions: linear methods Part V. Predicting Properties of Matter from Electronic Structure - Recent Developments: 18. Quantum molecular dynamics (QMD) 19. Response functions: photons, magnons ... 20. Excitation spectra and optical properties 21. Wannier functions 22. Polarization, localization and Berry's phases 23. Locality and linear scaling O (N) methods 24. Where to find more Appendixes References Index.

Electronic Structure: Basic Theory and Practical Methods

First-principles calculations have evolved from mere aids in explaining and supporting experiments to powerful tools for predicting new materials and their properties. In the first part of this review we describe the state-of-the-art computational methodology for calculating the structure and energetics of point defects and impurities in semiconductors. We will pay particular attention to computational aspects which are unique to defects or impurities, such as how to deal with charge states and how to describe and interpret transition levels. In the second part of the review we will illustrate these capabilities with examples for defects and impurities in nitride semiconductors. Point defects have traditionally been considered to play a major role in wide-band-gap semiconductors, and first-principles calculations have been particularly helpful in elucidating the issues. Specifically, calculations have shown that the unintentional n-type conductivity that has often been observed in as-grown GaN cannot be a...

First-principles calculations for defects and impurities: Applications to III-nitrides

We present a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III–V semiconductors that have been investigated to date. The two main classes are: (1) “conventional” nitrides (wurtzite and zinc-blende GaN, InN, and AlN, along with their alloys) and (2) “dilute” nitrides (zinc-blende ternaries and quaternaries in which a relatively small fraction of N is added to a host III–V material, e.g., GaAsN and GaInAsN). As in our more general review of III–V semiconductor band parameters [I. Vurgaftman et al., J. Appl. Phys. 89, 5815 (2001)], complete and consistent parameter sets are recommended on the basis of a thorough and critical review of the existing literature. We tabulate the direct and indirect energy gaps, spin-orbit and crystal-field splittings, alloy bowing parameters, electron and hole effective masses, deformation potentials, elastic constants, piezoelectric and spontaneous polarization coefficients, as well as heterostructure band offsets. Temperature an...

Band parameters for nitrogen-containing semiconductors

V2+ Impurity States in ZnS by the Green's Function Method

We present theory of coherent tunneling in all-semiconductor heterostructures containing (Ga,Mn)As ferromagnetic layers. The model combines multi-orbital tight-binding approach with Landauer-Buttiker formalism. Prompted by experimental results on resonant tunneling (RTD), tunneling magnetoresistance (TMR), and anisotropic magnetoresistance (TAMR), we describe the applicability of our theory to asses the magnitude as well as the angular and bias dependencies of the spin current in these devices. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Theory of spin-dependent tunneling and resonant tunneling in layered structures based on (Ga,Mn)As

In the present paper, we assess the accuracy of popular and widely used approaches based on density functional theory by relating them to the most accurate at present quantum Monte Carlo calculations. As the test case, we consider the relative stability of small SinCm isomers. We find out that none of the studied DFT approaches employing local, semilocal, or even hybrid functionals are able to predict correctly the relative stability of the isomers.

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Quantum Monte Carlo vs. Density Functional Methods for the Prediction of Relative Energies of Small Si-C Clusters

The morphology, charge distribution, and stability of interfaces in the diamond/c-BN and 3C-SiC/zb-GaN heteropolar junctions grown along the [1 1 1] and [0 0 1] crystallographic directions are obtained from first principles calculations in the framework of density functional theory. It is shown that reconstructions occurring in 3C-SiC/zb-GaN by the Si and C atoms in the abrupt C–Ga, Si–Ga and Si–N, C–N interfaces, respectively, induce charge compensation and stabilize these interfaces. On the contrary, a mutual exchange of these two compensating atoms destroys the energetical stability of the discussed interfaces. Reconstruction of the C–N interface type, common for 3C-SiC/zb-GaN and diamond/c-BN by C atom, is energetically favourable in both heterostructures and it is accompanied by a similar charge transfer in [1 1 1], while the reconstruction of the analogous C–Ga and C–B interfaces is unfavourable in both cases. Finally, it is demonstrated that in the diamond/c-BN junctions grown along the [0 0 1] crystallographic direction, the most stable interfaces are of the C–N type with reconstruction in the uppermost substrate carbon layer.

https://iopscience.iop.org/article/10.1088/2053-1591/aa6966/pdf

Comparative ab initio studies on morphology and stability of the C/BN and SiC/GaN heterostructure interfaces

We give a survey of recent efforts to find efficient light emitters based upon crystalline group IV materials by theoreticalmeans. While Si-based superlattices can readily be made into direct gap materials, their matrix elements for opticaltransitions do remain small, and even if polar intra-layers are added do they nowhere near match the yardstick set byGaAs. More promising properties show up in strained Ge and the relatively novel GeSn strained layer superlattices. 1. Introduction With an ever increasing demand for integrated opto-electronic circuits it seems only natural to take a close look on whether and how Si, the material of choice for most electronic devices - thanks to its low price, relative ease of processing and consequently highly developed processing techniques - can be transformed into an efficient opticalemitter, too.Unfortunately, the fundamental gap in pure crystalline Si is not direct in k-space, thus allowing only weak radiativerecombinations of electrons and holes via indirect transitions. A prime method in recent years of tailoring the propertiesof a Si-based materials to specific needs has been to alloy Si with its close relative, Ge, and to build strained-layersuperlattices [SLS] from different SiGe alloys'4

Jacek A. Majewski

Papers

V2+ Impurity States in ZnS by the Green's Function Method

Theory of spin-dependent tunneling and resonant tunneling in layered structures based on (Ga,Mn)As

Quantum Monte Carlo vs. Density Functional Methods for the Prediction of Relative Energies of Small Si-C Clusters

Comparative ab initio studies on morphology and stability of the C/BN and SiC/GaN heterostructure interfaces

Light emission from ordered group-IV materials: concepts and prospects