January 30, 1998

Results of million-atom Quantum Dot simulations performed on the Cray T3E at NERSC by Alex Zunger's group at the National Renewable Energy Laboratory in Golden, Colo., will appear on the cover of the February issue of the Materials Research Society Bulletin (http://www.sst.nrel.gov/research/InAs.html)

Andrew Canning of NERSC's Scientific Computing Group has been working with Zunger, Andrew Williamson and Lin-Wang Wang at NREL to develop a parallel code that can perform quantum mechanical simulations of systems of up to a million atoms (for a small number of electronic states) on the 544-processor T3E at NERSC, using the "Folded Spectrum Method" developed by Dr. Zunger's group. Only the T3E has a sufficiently high bandwidth of communications for 512-processor runs to perform the global communications required to scale this type of problem to a million atoms.

The quantum dots, currently being studied as potential components in the next generation of electronic devices, range in size from a few thousand to a few million atoms. The power of the T3E allows us, for the first time, to simulate these actual quantum dots rather than having to try and extrapolate their properties from smaller, less accurate simulations.

Quantum dots have the important property that they can confine electrons at precise energy levels which can be controlled by the shape and size of the dot. Therefore, a single electron could store information and act as a memory unit for a computer. These new computers would then have memory units of atomic size and processing speeds much faster than present computers. Recent advances in nanotechnology have allowed the construction of chips that contain large numbers of these quantum dots although the process is still at the experimental stage. Quantum dots can also be used for lasers whose frequency of emission can be controlled very accurately from the construction of the dot, and whose threshold current is orders of magnitude lower than conventional lasers.