@Article{icces.2011.019.077,
AUTHOR = {Nobuko  Ohba, Shuji  Ogata},
TITLE = {Progresses of the hybrid quantum-classical simulation: development of O(N)-DFT method and application to Li-diffusion in graphite},
JOURNAL = {The International Conference on Computational \& Experimental Engineering and Sciences},
VOLUME = {19},
YEAR = {2011},
NUMBER = {3},
PAGES = {77--78},
URL = {http://www.techscience.com/icces/v19n3/32835},
ISSN = {1933-2815},
ABSTRACT = {We have been developing the concurrent-type, hybrid quantum-classical simulation scheme for various atomic processes at liquid-solid interfaces [1]. In this scheme, the density-functional theory (DFT) method is applied to the "quantum" region to calculate the electronic structure; while the semi-empirical inter-atomic potential, to the "classical" region. In this talk we review its recent developments both from methodology and application viewpoints.  <br/>

In the hybrid simulation, the DFT method that is applied at each time-step to a cluster of typically a hundred atoms (i.e., the QM region) consumes most of the computation power. It is highly desirable to develop a less compute-intensive scheme without degrading the accuracy of the original O(N3)-DFT. Motivated by this, we develop a novel O(N)-type, real-space DFT method for parallel machines. In this method a total QM region is describe as the superposition of the DFT sub-regions by introducing the density-template potential to each Kohn-Sham equation in addition to the embed-potential used in existing papers. The accuracy and performance checks are presented. <br/>

Theoretical understanding of the Li-diffusion is crucial for further advancement of the Li-ion battery. It is known experimentally that the Li distribution in the Li-graphite intercalation compound shows transitive stages as its density increases, called the stage structure; in each stage the Li-rich and poor layers align in a unique sequence. The Li-diffusivity varies by orders of magnitude depending on the stage. The open problems include the possible relation of the formation kinetics of the stage structure and the Li-diffusivity. Since the graphite expands locally by 10% when the Li is inserted, we may expect significant influence of the long-ranged, stress-field on the Li diffusivity. We tackle this problem by applying directly the hybrid QM-CL simulation method.},
DOI = {10.3970/icces.2011.019.077}
}