LAMMPS and the LATTE density functional tight-binding code

C. F. A. Negre (1), R. T. Perriot (1), M. J. Cawkwell (1), A. M. N. Niklasson (1) and S. J. Plimpton (2)

LATTE is a molecular dynamics package based around self-consistent-charge density functional tight binding theory (DFTB) 1, 3, 2. It enables the linear scaling construction of the density matrix by applying a recursive Fermi operator expansion in sparse matrix algebra 4. It also provides an implementation of the extended Lagrangian Born-Oppenheimer molecular dynamics formalism (XL-BOMD) which provides long-term energy conservation in microcanonical trajectories while removing the expensive, iterative self-consistent eld procedure at each time step. 5. As part of an exascale computing project 6, the LATTE code now can be compiled as a library and bindings for integration with the LAMMPS molecular dynamics code 7 have been developed. With this implementation it is possible to most of the LAMMPS functionalities with forces calculated at the DFTB level of theory. Results that highlight the power of the combined codebases will be presented. These include geometry optimizations, linear scaling molecular dynamics simulation of several thousand atoms, and the determination of transition barriers for bond breaking using the nudged elastic band method.

1 M. Elstner, D. Poresag, G. Jungnickel, J. Elsner, M. Haugk, T. Frauenheim, S. Suhai, and G. Seifert, \Self-consistent-charge density-functional tight-binding method for simulations of complex materials properties," Phys. Rev. B, vol. 58, p. 7260, 1998.

2 N. Bock, M. J. Cawkwell, J. D. Coe, A. Krishnapriyan, M. P. Kroonblawd, A. Lang, E. M. Saez, S. M. Mniszewski, C. F. A. Negre, A. M. N. Niklasson, E. Sanville, M. A. Wood, and P. Yang, \LATTE," 2008. https://github.com/lanl/LATTE.

3 M. J. Cawkwell and A. M. N. Niklasson, \Energy conserving, linear scaling Born-Oppenheimer molecular dynamics," J. Chem. Phys., vol. 137, p. 134105, 2012.

4 A. M. N. Niklasson, \Expansion algorithm for the density matrix," Phys. Rev. B, vol. 66, p. 155115, 2002.

5 A. M. N. Niklasson, \Extended born-oppenheimer molecular dynamics," Phys. Rev. Lett., vol. 100, p. 123004, 2008.

6 \The exascale computing project," 2017. https://exascaleproject.org/exascale-computing-project/.

7 S. Plimpton, \Fast parallel algorithms for short-range molecular dynamics," J. Comp. Phys., vol. 117, p. 1, 1995.