From owner-chemistry@ccl.net Mon Apr 14 15:08:00 2014 From: "Morgan Durand durand_morgan ~ yahoo.fr" To: CCL Subject: CCL: Negative Ionization potential Message-Id: <-49916-140414093220-19746-t9NOwPpyeozKKpXPj1d3xQ##server.ccl.net> X-Original-From: "Morgan Durand" Date: Mon, 14 Apr 2014 09:32:19 -0400 Sent to CCL by: "Morgan Durand" [durand_morgan:+:yahoo.fr] Dear All, I have to compute ionization potential for neutral or ionic forms via DFT. I benchmarked several functional and basis set based on litterature data (Fu & al., JACS 2005, 127, 7227-7234). Finally, I used TURBOMOLE associated with PBE0 def2-TZVPPD for final energy calculation. Computed IP are very close to the litterature data (both experimental and calculated). Lately, I computed IP for almost 100 compounds. For some of them, DFT calculation leads to negative ionization potential. What does it means ? That something went wrong in my calculation ? Or that these compounds can't be ionized ? Anything else ? Thanks in advance, Best Regards, Morgan From owner-chemistry@ccl.net Mon Apr 14 15:43:00 2014 From: "Bhaskar Vinay Kamble bkamble a rhrk.uni-kl.de" To: CCL Subject: CCL:G: GAMESS-How are the spin orbitals categorized in the log file? Message-Id: <-49917-140414101203-25586-1gdwnzn4wJcdzL5TdQT5Qg_._server.ccl.net> X-Original-From: "Bhaskar Vinay Kamble" Date: Mon, 14 Apr 2014 10:12:02 -0400 Sent to CCL by: "Bhaskar Vinay Kamble" [bkamble]_[rhrk.uni-kl.de] I'm using the EOMCCSD routine in GAMESS to find the excited states of the Ni3 molecule. Here are some double excitations in a spin-singlet excited state from the log file: R2= -0.0526323393 FOR IA,JB -> AA,BB = 41 42 43 47 R2= -0.0730801299 FOR IA,JB -> AA,BB = 41 42 47 43 R2= -0.0730801374 FOR IA,JB -> AA,BB = 42 41 43 47 R2= -0.0526323393 FOR IA,JB -> AA,BB = 42 41 47 43 The 2 in R2 implies a double excitation with I,J -> A,B. I assume the A in IA and the second A in AA implies spin-alpha (up-spin) while the B in JB and the second B in BB implies spin-beta (down-spin) - but I am not sure. My question is about the convention followed in enumerating the above spin terms. One possible way of creating a spin singlet from a double excitation is ((IA -> AA)+(IB -> AB))*((JA -> BA)+(JB -> BB)) - at least this is what is done in GAUSSIAN. This gives the terms (IA,JA -> AA,BA), (IA,JB -> AA,BB), (IB,JA -> AB,BA) and (IB,JB -> AB,BB). Is this is convention being followed here? If so, then I do not understand why only the IA,JB -> AA,BB terms are listed here and not the rest. If it is not the convention, then I would be grateful if someone can tell me what it is. Also, the simultaneous presence of 41A,42B -> 43A,47B, AND 41A,42B -> 47A,43B with different coefficients (first and second lines) is confusing me. With best regards, Bhaskar Kamble Building: 46. Room: 508 Department of Physics, University of Kaiserslautern, 67663 Kaiserslautern, Germany Email: bkamble^^rhrk.uni-kl.de From owner-chemistry@ccl.net Mon Apr 14 16:19:00 2014 From: "Susi Lehtola susi.lehtola#alumni.helsinki.fi" To: CCL Subject: CCL: Negative Ionization potential Message-Id: <-49918-140414161531-25743-I4C9u9aIYJMTTMfvIPc4QA*server.ccl.net> X-Original-From: Susi Lehtola Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII Date: Mon, 14 Apr 2014 23:15:23 +0300 MIME-Version: 1.0 Sent to CCL by: Susi Lehtola [susi.lehtola..alumni.helsinki.fi] On Mon, 14 Apr 2014 09:32:19 -0400 "Morgan Durand durand_morgan ~ yahoo.fr" wrote: > Sent to CCL by: "Morgan Durand" [durand_morgan:+:yahoo.fr] > Dear All, > > I have to compute ionization potential for neutral or ionic forms via DFT. I benchmarked several functional and basis set based on litterature data (Fu & al., JACS 2005, 127, 7227-7234). Finally, I used TURBOMOLE associated with PBE0 def2-TZVPPD for final energy calculation. Computed IP are very close to the litterature data (both experimental and calculated). > > Lately, I computed IP for almost 100 compounds. For some of them, DFT calculation leads to negative ionization potential. > > What does it means ? That something went wrong in my calculation ? Or that these compounds can't be ionized ? Anything else ? The ionization potential (IP) is the energy necessary to pull out an electron from a system, away to infinity. A negative IP simply means that the electron is not bound: it would instantaneously fly away from the system. This can either be due to the basic physics/chemistry (e.g. a bad geometry), or an artifact of the calculation (e.g. insufficient basis set or level of theory, or calculation wasn't converged). You don't specify which ionization potential or the actual method you use (Delta-SCF?), so I can't really tell what's the case here. But if I were you, I'd check the geometries first. -- --------------------------------------------------------------- Mr. Susi Lehtola, PhD Research Associate susi.lehtola(-)alumni.helsinki.fi Department of Applied Physics http://www.helsinki.fi/~jzlehtol Aalto University Finland --------------------------------------------------------------- Susi Lehtola, FT Tutkijatohtori susi.lehtola(-)alumni.helsinki.fi Fysiikan laitos http://www.helsinki.fi/~jzlehtol Aalto-yliopisto ---------------------------------------------------------------