From owner-chemistry@ccl.net Sun Dec 6 14:07:01 2009 From: "Geoffrey Hutchison geoffh{:}pitt.edu" To: CCL Subject: CCL:G: how to build a polythiophene unit cell for a pbc gaussian calculation Message-Id: <-40871-091206140017-22972-NDaxASCS/q4W9rW4NM6U1Q[A]server.ccl.net> X-Original-From: Geoffrey Hutchison Content-transfer-encoding: quoted-printable Content-type: text/plain; charset=iso-8859-1 Date: Sun, 06 Dec 2009 13:21:05 -0500 MIME-version: 1.0 (Apple Message framework v1077) Sent to CCL by: Geoffrey Hutchison [geoffh]=[pitt.edu] > I will be pleased if you can point me to a (step by step) guide on how = to build a polythiophene=20 > unit cell for a pbc gaussian calculation, using GaussView or any other = program. > Please note: I don=B4t need only the input file, I want to learn how = to build the unit cell. This was easy enough to do, I wrote a quick walkthrough using Avogadro. http://avogadro.openmolecules.net/wiki/Tutorials:Polymer_Unit_Cell It only takes a few minutes if you're willing to start from the = MM-optimized geometry. To be more accurate, I'd start with a = DFT-optimized oligomer and "chop out" a central pair of rings. The main thing is that the Align tool in Avogadro allows you to put one = atom at the origin and project another atom into a particular Cartesian = axis. This is useful whenever you want to set a specific frame of = reference for molecular coordinates. Best regards, -Geoff --- Prof. Geoffrey Hutchison Assistant Professor, Department of Chemistry University of Pittsburgh http://hutchison.chem.pitt.edu/ Office: (412) 648-0492 From owner-chemistry@ccl.net Sun Dec 6 18:12:01 2009 From: "Stephen Bowlus chezbowlus__comcast.net" To: CCL Subject: CCL: van't Hoff factor Message-Id: <-40872-091206175413-1606-3u75LiEG5MHT0i7ESU46DA[a]server.ccl.net> X-Original-From: Stephen Bowlus Content-Type: multipart/alternative; boundary=Apple-Mail-16-512482673 Date: Sun, 6 Dec 2009 14:54:00 -0800 Mime-Version: 1.0 (Apple Message framework v936) Sent to CCL by: Stephen Bowlus [chezbowlus(!)comcast.net] --Apple-Mail-16-512482673 Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit Are there some simple, structural rules of thumb (a qualitative SAR, if you will) that relate the van't Hoff factor to solution concentration? At infinite dilution, _i_ = number of particles possible from complete dissociation. From tables I have seen, it seems though, that different ions (and ion combinations) have different slopes in a plot of i vs [solute]. Is it possible to predict that slope for an ion/ion pair? Steve Bowlus --Apple-Mail-16-512482673 Content-Type: text/html; charset=US-ASCII Content-Transfer-Encoding: 7bit Are there some simple, structural rules of thumb (a qualitative SAR, if you will) that relate the van't Hoff factor to solution concentration? At infinite dilution, _i_ = number of particles possible from complete dissociation. From tables I have seen, it seems though, that different ions (and ion combinations) have different slopes in a plot of i vs [solute]. Is it possible to predict that slope for an ion/ion pair?

Steve Bowlus

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