Abstracts and Talk Materials:
September 29-October 3, 2008
Mathieu Lewin (Université de Cergy-Pontoise) http://www.u-cergy.fr/lewin/
Exact embedding of local defects in crystals
Wed Oct 01 15:20:00 - 16:10:00
By means of rigorous thermodynamic limit arguments, we derive a new
variational model providing exact embedding of local defects in insulating or
semiconducting crystals. A natural way to obtain variational discretizations
of this model is to expand the perturbation of the periodic density matrix
generated by the defect in a basis of precomputed maximally localized Wannier
functions of the host crystal. This approach can be used within any
semi-empirical or Density Functional Theory framework. This is a joint work
with Eric Cancès and Amélie Deleurence (Ecole Nationale des Ponts et
Chaussées, France).
John E. Pask (Lawrence Livermore National Laboratory) http://physci.llnl.gov/Research/Metals_Alloys/People/Pask/
Partition-of-unity finite-element approach for large, accurate ab initio electronic structure calculations
Fri Oct 03 11:15:00 - 12:05:00
Principle Collaborator:
Natarajan Sukumar
(University of California, Davis) Over the past few decades, the planewave (PW) pseudopotential method has established itself as the dominant method for large, accurate, density-functional calculations in condensed matter. However, due to its global Fourier basis, the PW method suffers from substantial inefficiencies in parallelization and applications involving highly localized states, such as those involving 1st-row or transition-metal atoms, or other atoms at extreme conditions. Modern real-space approaches, such as finite-difference (FD) and finite-element (FE) methods, can address these deficiencies without sacrificing rigorous, systematic improvability but have until now required much larger bases to attain the required accuracy. Here, we present a new real-space FE based method which employs modern partition-of-unity FE techniques to substantially reduce the number of basis functions required, by building known atomic physics into the Hilbert space basis, without sacrificing locality or systematic improvability. We discuss pseudopotential as well as all-electron applications. Initial results show order-of-magnitude improvements relative to current state-of-the-art PW and adaptive-mesh FE methods for systems involving localized states such as d- and f-electron metals and/or other atoms at extreme conditions.This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
|
