## Firefly and PC GAMESS-related discussion club

Learn how to ask questions correctly

** Re^2: Geometry optimization in two dimensions **
pejer

fajriah@gmail.com

My molecule is something like diazonium salt. Okay, I'll try the CS symmetry first. Thanks.On Mon Mar 3 '14 5:34pm, Thomas Pijper wrote

--------------------------------------------

>Dear Pejer,

>I do not know the geometry of your molecule, but is it possible to simply confine it to CS symmetry? That would be the simplest way to keep your molecule flat.

>

>

>Kind regards,

>Thom

>

>

>

>On Mon Mar 3 '14 8:33am, pejer wrote

>------------------------------------

>>Dear all.

>>I try to optimize my oligomer molecules without make it twisted (keep it flat) which means being optimize in two dimensions. I try:

>>1) using cartesian, by input the value of z coordinate cartesian into 0.00000000 for every atoms, then freeze this z of every atoms.

>>Although manual said that Cartesian couldn't be freezed, I found it on the contrary in another place in this web (classic.chem.msu.su/gran/gamess./marek/en/.../PCG-Tutorial-Usage.pdf) and this works for benzene (consists of 18 atoms), but fails for larger molecules (consists of 50 atoms).

>>2) using z-matrix, by input value of dihedral angles for every atoms into 0 or 180 degrees, then freeze this dihedral of every atoms.

>>I've tried:

>>- input every dihedral angles (using format in manual) in IFREEZ, fails when input for 49 dihedral angles, but succeed when input for 1 dihedral angle

>>- input every dihedral angles in IFZMAT, but it showed error messages "BAD ZMAT INPUT". Also, the DLC couldn't be performed.

>>

>>

>>I want to ask and ask for any suggestion,

>>1) Is there any problem in my input? Is there any limitation number of freezing atom/variable? Is there another menu that I could add?

>>2) Is there another strategy to optimize large molecules and keep it flat (optimize in 2D)? I work with molecules consists of n*50 atoms, the same molecules of other persons on a publication which using GAUSSIAN 03 package. They succeed to optimize oligomer in 2D.

>>Best regards,

>>Pejer

Tue Mar 4 '14 5:31am

This message read **553** times