Good questions...In grad school we often sat around and questioned at what point would the nano crystal structure no longer control the properties of the solid. Just how many atoms does it take to make a crystal solid? At what point would the material behave like an ordered amorphous material? Would it be visco elastic? Would it have a Tg? Would the structure have enough energy to hold a two dimensional defect? What would be the effect on the well understood crystal structures that have a strong dependence on the valance state, ie the spinels and ABO3's ? Yes this should be a good discussion.....anyone? Rob -----Original Message----- From: mems-talk-admin@memsnet.org [mailto:mems-talk-admin@memsnet.org]On Behalf Of Ivan Oleynik Sent: Tuesday, July 09, 2002 11:16 AM To: mems-talk@memsnet.org Subject: [mems-talk] NEMS: Critical questions to atomic scale theory Dear Colleagues, I am not involved in NEMS/MEMS research but has been very excited of NEMS area after reading several review papers in popular science press. I was trying to understand an importance of atomic structure in NEMS. My impression is that when dimensions of NEMS devices approach the size of several dozens of atoms across, surface effects including adsorbates, point defects inside the material and mechanical energy dissipative processes will influence in substantial way the mechanical energy dissipation and other characteristics of NEMS. When I looked at more specialized literature I found that most of MEMS/NEMS modeling was done by finite-element methods. There are couple of papers trying to marry finite-elements with atomistic theory but they address mainly classical mechanical problems such as crack propagation. I would like to hear from experimentalists and NEMS practitioners what are in their view the challenges to atomic scale theory that can only be addressed by using atomic scale modeling techniques such as molecular dynamics or first-principles quantum mechanics. Thanks, Ivan Oleynik ------------------------------------------------------------------------ Ivan I. Oleynik E-mail : oleynik@chuma.cas.usf.edu Department of Physics University of South Florida 4202 East Fowler Avenue Tel : (813) 974-8186 Tampa, Florida 33620-5700 Fax : (813) 974-5813 ------------------------------------------------------------------------ _______________________________________________ MEMS-talk@memsnet.org mailing list: to unsubscribe or change your list options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk Hosted by the MEMS Exchange, providers of MEMS processing services. Visit us at http://www.memsnet.org/