Title: Nano is Big: A First-Principles Electronic Structure Viewpoint

Speaker: Normand Modine

Date/Time: Wednesday, July 26, 2006, 3:00 – 4:00 pm (MST)

Location: Building 980, Room 95 (Sandia NM), videoconferenced to Building 940, Auditorium (Sandia CA)

Brief Abstract: To most scientists, the nanoscale represents the frontiers of smallness.  In contrast, from the perspective of the computational scientist performing ab initio electronic structure calculations, the nanoscale is challenging because it is larger than previously considered systems.  Electronic bonding, which is the dominant mechanism of interaction at the atomic scale, does not result in substantial interactions over distances of several nanometers.  Instead, longer-range interactions, arising from such phenomena as electromagnetism, strain, and electronic tunneling, are dominant.  A key challenge in understanding the unique phenomena that occur at the nanoscale is to identify the dominant interactions at these length scales and to quantify how they couple to both the nanoscale structure and the local atomic structure of the system.  We will discuss several examples that shed light on this challenge, as well as, some of the difficulties that arise in capturing nanoscale interactions using electronic structure methods.  Recent work on extending electronic structure techniques to overcome some of these problems will be reported.  We will emphasize calculations for semiconductor defects, alloys, and surfaces, where we have been able to make contact with experiment, and suggest likely areas for future experimental interaction.

CSRI POC: Robert Hwang, (505) 844-5852