From owner-chemistry@ccl.net Fri Nov 7 02:10:01 2008 From: "Gianluca Santarossa gianluca.santarossa-$-chem.ethz.ch" To: CCL Subject: CCL:G: Relaxed scan using GDIIS with Gaussian Message-Id: <-38050-081106082605-4359-rFu2R4IyGHa40ZIPBNn9dw-#-server.ccl.net> X-Original-From: "Gianluca Santarossa" Date: Thu, 6 Nov 2008 08:26:00 -0500 Sent to CCL by: "Gianluca Santarossa" [gianluca.santarossa^chem.ethz.ch] Dear CCL subscribers, I am trying to run a relaxed scan simulation of a molecule at PM3 level using Gaussian03. In order to make the geometry converge during the optimization I need to use the GDIIS algorithm. When the GDIIS option is activated, the program is only performing the first geometry optimization, and then it exits instead of moving the dihedral. This is the relevant part of the input: $RunGauss #P PM3 Opt(Z-matrix,tight,GDIIS) gfinput gfprint IOP(6/7=3) pop=full Theta scan of KDO disaccharide ! [cut] ... here comes the z-matrix ... dih9 0.000 S 35 10.0 [cut] ... here are more z-matrix parameters ... When only the parameter Opt=Z-matrix is used, the scan is performed correctly. The 'Initial Parameters' section of the output shows that the 'Scan' is on: [cut] ! cco9 109.737 estimate D2E/DX2 ! ! dih9 0.0 Scan ! ! cc10 1.5379 estimate D2E/DX2 ! [cut] However, adding the GDIIS options to the input - Opt(Z-matrix,GDIIS) - results in a geometry optimization that stops without the scan. Apparently, the program redefines the Z-matrix, as it is shown in the output, and could not scan anything: [cut] ---------------------------- ! Initial Parameters ! ! (Angstroms and Degrees) ! -------------------------- -------------------------- ! Name Definition Value Derivative Info. ! --------------------------------------------------------------------- ! R1 R(1,2) 1.4317 estimate D2E/DX2 ! ! R2 R(1,6) 1.4288 estimate D2E/DX2 ! [cut] May you please suggest me how to run a relaxed scan using the GDIIS optimizer? Regards, Gianluca