Planewave pseudopotential method
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Figure 1. A schematic representation of a hybrid algorithm developed for P3MD code that best uses the data locality for the electron wavefunction while maintains the flexibility of using a plane-wave basis. Implementation of the hybrid QMD method for next-generation petascale parallel platforms such as BG/P extends our capability to applications such as two-phase simulations of pressure-dependent melt curves for d- and f-electron metals. In our hybrid QMD method using plane-waves as the basis functions, the Kohn-Sham equations are solved by distributing each wave-function, which is represented by spin, k-point, band, Fourier and real space components, to a group of nodes. A custom parallel 3D FFT routine, comparable with the standard FFTW3, has been implemented so the Poisson equation can be solved in parallel over a cluster of nodes (up to 1024 nodes). The total execution time per self-consistent field (SCF) step as a function of number of processors on BG/L shows a good scalability with efficiency up to 74% on 16k nodes.

Planewave Pseudopotential (PP) Method


Lin Yang, Randy Hood

A planewave pseudopotential (PP) code that can perform ab-initio quantum-molecular-dynamics (QMD) simulations as well as static structural optimization has been developed and implemented on LLNL ASC platforms and Linux clusters. The most recent development is the implementation of a hybrid method that is to target the next generation petascale massively parallel platforms such as BG/P machine (Figure 1). This code allows for the calculation of density-functional-theory total energies, forces and stresses with an algorithm based on the pre-conditioned conjugate-gradient method and uses a planewave basis set and norm-conserving pseudopotentials [1]. One advantage of our PP code is that it has been shown to have an accuracy close to the all-electron FP-LMTO method for many applications [2], and yet is still fast enough to treat hundreds of atoms. The portability and accuracy of this code make it a desirable first-principles simulation tool in the study of complex molecular, liquid, and solid-state systems. Applications for this P3MD code include the calculation of free energies, search for structural minima, and ab-initio QMD simulation of quantum liquids in compressed and expanded systems [3].

REFERENCES

  1. L. H. Yang, Advanced Quantum-level Materials Design, in Industrial Strength Parallel Computing, edited by A. Koniges, (Morgan Kaufmann, San Francisco, 2000), p. 297.
  2. P. Söderlind, L. H. Yang, and J. A. Moriarty, "First-principles formation energies of monovacancies in bcc transition metals," Phys. Rev. B 61, 2579 (2000).
  3. M. Ross, L. H. Yang, and W.-C. Pilgrim. "Simulations of liquid Rubidium near the critical density," Phys. Rev. B 74, 212302 (2006).
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Maintained by Robert E. Rudd -- Last updated on 12 February 2007.
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