From owner-chemistry@ccl.net Sun Oct 18 08:21:01 2009 From: "Mikael Johansson mikael.johansson!^!helsinki.fi" To: CCL Subject: CCL: Summary: Total electron density cusps outside nuclei Message-Id: <-40487-091018081934-500-2LeB1G4IdIaGmlh6ILO9IA:_:server.ccl.net> X-Original-From: Mikael Johansson Content-ID: Content-Type: MULTIPART/MIXED; BOUNDARY="-696237619-632992821-1255867350=:2062" Date: Sun, 18 Oct 2009 15:19:08 +0300 (EEST) MIME-Version: 1.0 Sent to CCL by: Mikael Johansson [mikael.johansson * helsinki.fi] This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. ---696237619-632992821-1255867350=:2062 Content-Type: TEXT/PLAIN; FORMAT=flowed; CHARSET=ISO-8859-15 Content-Transfer-Encoding: 8BIT Content-ID: Hello All! About two weeks ago I sent the following question to the list (edited for brevity): On Tue, 6 Oct 2009, Mikael Johansson wrote: > Does someone remember seeing an article where the existence of cusps in the > total electron density were found in between the atomic positions? [...] > So if someone could point me to this paper, or any other article where > density cusps in the "middle" of a nuclear framework are discussed, I would > become very happy :-) I got several answers to my question, for which I am very grateful (and happy). First, let me thank those who answered, in order of appearance in my inbox: Jamie Platts, Andreas Krapp, Steve Williams, Serguei Patchkovskii, Eduard Matito, Adam Kubas, N. Sukumar, James Justin Robinson: thank you! Then on to the summary: The right keywords to look for are non-nuclear maxima (NNM) and/or non-nuclear attractors (NNA). From the suggested references, it seems that _maxima_ in the electron density have indeed been found outside nuclei, although there still seems to be a minor dispute whether these are really maxima or artefacts. Litium systems were apparently among the first systems where these were noticed, later several other systems have been suggested. However, the maxima found to date are not _cusps_ of the electron density, as Serguei Patchkovskii pointed out. There also seems to be something of a consensus that only point charges could give rise to these. Eduard Matito pointed me to the paper of Tosio Kato (1957) where this is discussed. The original reason for my question was E. Bright Wilson's argument (1965) (as an alternative to Hohenberg-Kohn 1) that the electron density does uniquely define the external potential for a Coulombic system, and thus > from the electron density alone, the Hamiltonian is completely defined, as will the wave function be. This argument relies on the assumption that cusps can only be present at the locations of the nuclei (or at least that other hypothetical cusps can be identified as non-nuclear cusps). Now, I'm probably just too sceptical a person, but I'm still not 100% sure that some weird electronic interactions couldn't give rise to something that looks like cusps also at other places than nuclei, or at least very close to "cusps" arising from real, non-pointlike nuclei. But for all practical purposes, I do believe that Wilson's argument is valid. At the end of this mail, I have compiled a list of all the references that I was given. Already the titles give a nice overview of what has been discussed in the literature. Have a nice day, Mikael J. http://www.iki.fi/~mpjohans/ Suggested references: Gatti et al, "Charge density topological study of bonding in lithium clusters Part I: Planar Lin clusters (n=4, 5, 6)", TCA 72 (1987) 433. Cao et al, "On the presence of non-nuclear attractors in the charge distributions of Li and Na clusters", CPL 141 (1987) 380. Cioslowski, "Nonnuclear Attractors in the Li2 molecule", JPC 94 (1990) 5496. Cooper, "A molecular catastrophe", Nature 346 (1990) 796. Bader, "Atoms in Molecules: A Quantum Theory" (1990) pp. 43 and 297. Iversen et al, "Experimental evidence for the existence of non-nuclear maxima in the electron-density distribution of metallic beryllium. A comparative study of the maximum entropy method and the multipole refinement method", Acta Cryst. B51 (1995) 580. Bader and Platts, "Characterization of an F-center in an alkali halide cluster", JCP 107 (1997) 8545. Pendás et al, "Non-nuclear Maxima of the Electron Density", PRL 83 (1999) 1930. Madsen et al, "On the existence of non-nuclear maxima in simple metals", JCP 117 (2002) 8030. Luaña et al, "Non-nuclear maxima of the electron density on alkaline metals", JCP 119 (2003) 6341. Timerghazin and Peslherbe, "Non-nuclear attractor of electron density as a manifestation of the solvated electron", JCP 127 (2007) 064108. ---696237619-632992821-1255867350=:2062-- From owner-chemistry@ccl.net Sun Oct 18 10:05:01 2009 From: "Alex Rudn rudikk99#%#yahoo.com" To: CCL Subject: CCL: scan Message-Id: <-40488-091018100328-4458-GHv0bik0f6ecIrij27x/Sg : server.ccl.net> X-Original-From: "Alex Rudn" Date: Sun, 18 Oct 2009 10:03:24 -0400 Sent to CCL by: "Alex Rudn" [rudikk99%%yahoo.com] Dear colleges, we are all familiar with a simple case of relaxed potential energy surface scan: P HF/6-31G(d) scan=opt nosymm H2O2 rotational potential 0. to 180., HF/6-31G(d) level internal coordinates 0 1 H1 O2 1 r2 O3 2 r3 1 a3 H4 3 r2 2 a3 1 d4 r2=1.0 r3=1.3 a3=110. d4=0.0 S 18 +10.0 here only dihedral angle of H atom moves. What if (and that;s my case) I have more complicated geometry, such as H | H2N- H2C - C = O and I want to see the energy difference when the whole C(O)H group rotates around C-C axes. That means I have to specify rotation of dihedral N-C-C-O - that gives me N-C-C-H staying still and overlay O to H sooner or later. What's the solution? I appreciate any useful comments. PS I considered an option of scanning of both dihedral - that gives me tans of useless info and dramatic spend of time. Best regards, Alex From owner-chemistry@ccl.net Sun Oct 18 14:23:00 2009 From: "Cory Pye cpye]=[ap.smu.ca" To: CCL Subject: CCL: scan Message-Id: <-40489-091018142009-5560-TB9V2vmzotPa2UZSNkMVPA^^server.ccl.net> X-Original-From: Cory Pye Content-Type: TEXT/PLAIN; charset=US-ASCII Date: Sun, 18 Oct 2009 15:19:51 -0300 (ADT) MIME-Version: 1.0 Sent to CCL by: Cory Pye [cpye+/-ap.smu.ca] Hi, This can be done by careful specification of the z-matrix, as in: C1 C2 C1 C2C N C2 NC C1 NCC H2A C2 H2AC C1 H2ACC N H2ACCN H2B C2 H2BC C1 H2BCC N H2BCCN H3A N H3AN C2 H3ANC C1 H3ANCC H3B N H3BN C2 H3BNC C1 H3BNCC O C1 OC C2 OCC N OCCN H1 C1 H1C O H1CO C2 H1COC C2C = 1.55 NC = 1.40 H2AC = 1.09 H2BC = 1.09 H3AN = 1.03 H3BN = 1.03 OC = 1.20 H1C = 1.06 NCC = 109.5 H2ACC = 109.5 H2BCC = 109.5 H3ANC = 105.0 H3BNC = 105.0 OCC = 120.0 H1CO = 120.0 H2ACCN = 60.0 H2BCCN = -60.0 H3ANCC = 60.0 H3BNCC = -60.0 (this might also be 180.0, depending on the desired amine conformation.) OCCN = 0.0 S 24 15.0 H1COC = 180.0 Note the definition of the aldehydic hydrogen w.r.t C1, O, and C2. As the OCCN angle is rotated, this hydrogen goes along for the ride! -Cory On Sun, 18 Oct 2009, Alex Rudn rudikk99#%#yahoo.com wrote: > > Sent to CCL by: "Alex Rudn" [rudikk99%%yahoo.com] > Dear colleges, > > we are all familiar with a simple case of relaxed potential energy surface scan: > > P HF/6-31G(d) scan=opt nosymm > > H2O2 rotational potential 0. to 180., HF/6-31G(d) level > internal coordinates > > 0 1 > H1 > O2 1 r2 > O3 2 r3 1 a3 > H4 3 r2 2 a3 1 d4 > > r2=1.0 > r3=1.3 > a3=110. > d4=0.0 S 18 +10.0 > > here only dihedral angle of H atom moves. What if (and that;s my case) I have more complicated geometry, such as > H > | > H2N- H2C - C = O > > and I want to see the energy difference when the whole C(O)H group rotates around C-C axes. That means I have to specify rotation of dihedral N-C-C-O - that gives me N-C-C-H staying still and overlay O to H sooner or later. > > What's the solution? > > > I appreciate any useful comments. > > PS I considered an option of scanning of both dihedral - that gives me tans of useless info and dramatic spend of time. > > Best regards, > > Alex> > ************* ! Dr. Cory C. Pye ***************** ! Associate Professor *** ** ** ** ! Theoretical and Computational Chemistry ** * **** ! Department of Chemistry, Saint Mary's University ** * * ! 923 Robie Street, Halifax, NS B3H 3C3 ** * * ! cpye[]crux.stmarys.ca http://apwww.stmarys.ca/~cpye *** * * ** ! Ph: (902)-420-5654 FAX:(902)-496-8104 ***************** ! ************* ! Les Hartree-Focks (Apologies to Montreal Canadien Fans)