Ravi, As far as I know, anything with a band gap is an insulator... The term "semiconductor" is generally employed only to discriminate insulators with a band gap below a certain value, say, 4 eV. So your ZnO wires are also insulators - provided, of course, they have a non-zero band gap from your calculations :)
Cheers, Marcos On Mon, Nov 30, 2009 at 4:14 PM, Ravi Agrawal < [email protected]> wrote: > Hi Chris/Andrei, > > Your ongoing discussion is interesting and quite insightful for me, as I am > also planning to pursue some polarization calculations. > > My system will be zinc oxide nanowires - with free surfaces and periodicity > induced along the length (modeling infinitely long wires). > I am wondering if the approach of calculating polarization using the > Berry-Phase approach (by employing Polarization Grids) is suitable for this > scenario. ZnO has a band gap and is semiconducting, but not an "insulator". > This question came up as the SIESTA manual suggests that Berry-phase > approach is suitable only for insulators. > > Please, shed some light on this issue as well, in lieu of your ongoing > discussion. > > Thanks, > Ravi > > Northwestern University > Evanston, IL 60208 - 3111 > > > > On Mon, Nov 30, 2009 at 9:03 AM, <[email protected]> wrote: > >> Dear Chris, >> I think you attempt to cheat the code and to overcome its >> naive protection against an attempt to calculate polarization >> on a metal system. What matters 12 or 13 silver atoms, >> a little bit metal is a metal, in the context given. >> Are you sure you are doing >> something reasonable even when "it performs the calculation!" ? >> Do you have a band gap in your silver-on-whatever system? >> The band gap is NEEDED for calculating the polarization, Berry phase or >> not. >> >> Best regards >> >> Andrei Postnikov >> >> > Thanks Andrei, >> > >> > I was trying to use the silver system as a simple example. What I'm >> truly >> > interested in calculating is the polarization in a polymer-metal >> > nanocomposite; and what I've found is that with a matrix of 400 atoms >> and >> > a >> > metal (i.e. silver) inclusion with an odd number of atoms (I tried with >> > 13) >> > then SIESTA won't do the polarization calculation: odd total number of >> > electrons. But if the inclusion is only 12 atoms, it performs the >> > calculation! I also tried giving the system a single positive charge >> but >> > to >> > no avail. >> > >> > Chris Rowan >> > M.Sc. Candidate >> > University of Victoria >> > Canada >> >> >
