*From*: Krzysztof Radacki <K.Radacki (+ at +) ic.ac.uk>*Organization*: Imperial College, London*Subject*: gaussian problems*Date*: Tue, 09 Jul 2002 14:13:41 +0100

Dear all, I have two question and one information concerning gaussian. 1) I wanted to perform an optimization with possibly slowest changing of geometry. The command line was as: #P OPT=(Redundant,CalcAll,StepSize=1,TIGHT) INT=(GRID=99590) I got an error: QPERR --- A SYNTAX ERROR WAS DETECTED IN THE INPUT LINE. #P OPT=(REDUNDANT,CALCALL,STEPSIZE=1,TIG ' What's wrong? On p.129 of User's reference one can find description of StepSize in Opt and I can't see why it shouldn't work. 2) However calculation of IR was already sometimes discussed on CCL I still have uneasy feeling. An example. I have a molecule with trigonal bipiramide (D3h) structure. I know however that minimum is distorted - both axial ligands are moved out of Z-axis in direction of one equatorial ligand (f.e.: ax-ax angle 160) and the equatorial are still co-planar (C2v). (I hope that you can imagin it from my description). Now: If I would distorte D3h structure to C2v with ax-ax angle 175 deg and optimized geometry with frozen ax-ax, should IR calculation have a one imaginary freq. narrowing ax-ax angle or not? If it gives me no Imag - hwat does it mean? One can find in books that vibrational analysis should be performed only on stationary point - if not it's meaningless. What sense has it if one makes such restriction? If I want to be sure that I'm in minimum should I repaet all symmetry bounded calculation (like above D3h) with NoSymm? 3) Last week I wanted to calculated some quite complicated molecules like CO or CCH2 and various level of theory. Everything was fine with DFT and MP2 but the same inputs didn't work for CCSD and CCSD(T). The input like: %MEM=1000MB %NPROC=2 %SAVE %CHK=CO-CCSD #P OPT=(CART,TIGHT) POP=FULL CCSD/6-311G(D,P) Gues=Read carbon monoxid 0 1 C 0.000000000000 0.000000000000 0.000000000000 O 0.000000000000 0.000000000000 1.126962524921 produced an error: Symbolic Z-matrix: Charge = 0 Multiplicity = 1 C 0. 0. 0. O 0. 0. 1.12696 Leave Link 101 at Fri Jul 5 17:23:43 2002, MaxMem= 13107200 cpu: 0.2 (Enter /usr/local/SW/g98/l114.exe) NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF- NUMERICAL EIGENVECTOR FOLLOWING MINIMUM SEARCH INITIALIZATION PASS ************************************************ ** ERROR IN INITNF. NUMBER OF VARIABLES ( 0) ** ** INCORRECT (SHOULD BE BETWEEN 1 AND 50) ** ************************************************ Error termination via Lnk1e in /usr/local/SW/g98/l114.exe. I was supprised that gaussian was looking for z-matrix even if I wrote opt=cart. I've repeated the calculation with opt=z-matrix and geometry: C O 1 r1 r1 = 1.126962524921 and gaussian succeed with Normal Termination. So probably I've found small bug. Thanks a lot in advance and best reagrds Krzysztof -- Dr. K.Radacki Department of Chemistry Catalysis and Advanced Materials Section Imperial College, London