Robert Rudd, Per Söderlind, Fred Streitz, Dave Richards

Vortices from a 9 billion atom simulation of shear flow in a molten aluminum-copper system [1]. Extremely large-scale MD simulations such as this fluid flow simulation require computationally efficient interatomic potentials.

Interatomic potentials form the basis for all classical molecular dynamics (MD) simulations. They determine the forces that the atoms experience in a simulation, and it is through them that material properties are specified. Potentials give the energy as functions of the spatial coordinates of the ions, with the electronic degrees of freedom integrated out. In this project we develop many-body potentials for high pressure applications based on ab initio calculations of the properties of atomic systems. We are interested in both high fidelity and high speed potentials for use in highly scalable parallel MD codes. Indeed, we rely on the extraordinary computational power of the LLNL supercomputers in order to reach systems with billions of atoms [1] and systems that demand very complicated, expensive potentials [2]. We also rely on the supercomputer resources to carry out extensive ab initio calculations for parameterization and verification of the potentials [3]. The flagship potentials for high pressure simulations are the Model Generalized Pseudopotential Theory (MGPT) potentials invented by John Moriarty [4]. Our potential development efforts are, at least initially, concentrating on potentials for strength and phase transformation applications in metals.

### Selected Publications

- "Micron-scale Simulations of Kelvin-Helmholtz Instability with Atomistic Resolution ," J.N. Glosli, K.J. Caspersen, D.F. Richards, R.E. Rudd, F.H. Streitz, and J.A. Gunnels, in Proc. Supercomputing 2007 (SC07), Reno, NV, Nov. 2007.
- "100+ TFlop Solidification Simulations on BlueGene/L," Frederick H. Streitz, James N. Glosli, Mehul V. Patel, Bor Chan, Robert K. Yates, Bronis R. de Supinski, James Sexton and John A. Gunnels, in Proceedings of Supercomputing 05 (SC05). Seattle, Washington, November 2005.
- As an example of prior LLNL work see: "Robust Quantum-Based Interatomic Potentials for Multiscale Modeling in Transition Metals ," J. A. Moriarty, L. X. Benedict, J. N. Glosli, R. Q. Hood, D. A. Orlikowski, M. V. Patel, P. Söderlind, F. H. Streitz, M. Tang and L. H. Yang, J. Mater. Res.
**21**, 563 (2006). - "Angular Forces and Melting in bcc Transition Metals: a Case Study of Molybdenum ," J.A. Moriarty, Phys. Rev. B
**49**, 124431 (1994).

Maintained by Lorin X. Benedict