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 > >
