Learn how to ask questions correctly

Siddheshwar Chopra

sidhusai@gmail.com

Dear Mridula,

You could also try tightening the DFT grid using LMAX and NRAD. Do check the manual. Also have a careful look at the structure, in case if you have not terminated the edges well.

Regards,

On Tue Jul 21 '15 4:54pm, Alex Granovsky wrote

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

>Dear Mridula Guin,

>you need to examine this frequency.

>The simplest way to do this is to use ChemCraft.

>Open your output file in ChemCraft and look at the problematic

>normal mode. You will be able to check if it is a vibration or

>rather a rotation or translation. If it is indeed a vibration,

>create a geometry that is displaced along this mode and re-optimize

>this new structure from the scratch.

>Kind regards,

>Alex Granovsky

>

>

>On Mon Jul 20 '15 7:50am, Mridula Guin wrote

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

>>Dearv Alex sir,

>>The magnitude is 33.04 cm-1.Please tell me how to get rid of this negative frequency.

>>On Mon Jul 20 '15 1:07am, Alex Granovsky wrote

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

>>>Hello,

>>>The excluded frequency is imaginary (this frequency is marked as

>>>negative in the printout section). This means that your structure

>>>is not a minimum on a PES but rather is a saddle point on a PES.

>>>What is the magnitude of the imaginary/negative frequency?

>>>Kind regards,

>>>Alex Granovsky

>>>

>>>

>>>On Fri Jul 17 '15 8:33am, Mridula Guin wrote

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

>>>>Dear firefly users

>>>>During performing frequency calculation, in the thermochemistry section for an optimized geometry I am getting an imaginary frequency which is excluded. My question is whether the structure is stable or not? You can have a look to the part of the logfile below. Please help me to understand this.

>>>>Thanks in advance..

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

>>>> THERMOCHEMISTRY AT T= 298.15 K

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

>>>>

>>>>

>>>>

>>>> USING IDEAL GAS, RIGID ROTOR, HARMONIC NORMAL MODE APPROXIMATIONS.

>>>> P= 1.01325E+05 PASCAL.

>>>> ALL FREQUENCIES ARE SCALED BY 1.00000

>>>> THE MOMENTS OF INERTIA ARE (IN AMU*BOHR**2)

>>>> 480.71546 2956.60067 3437.31425

>>>> THE ROTATIONAL SYMMETRY NUMBER IS 1.0

>>>> THE ROTATIONAL CONSTANTS ARE (IN GHZ)

>>>> 3.75084 0.60985 0.52456

>>>> 1 IMAGINARY FREQUENCY VIBRATION(S) IS(ARE) EXCLUDED

>>>> FROM THE FOLLOWING THERMOCHEMICAL ANALYSIS.

>>>> THE HARMONIC ZERO POINT ENERGY IS (SCALED BY 1.000)

>>>> 0.127532 HARTREE/MOLECULE 27990.070745 CM**-1/MOLECULE

>>>> 80.027708 KCAL/MOL 334.835932 KJ/MOL

>>>>

Tue Jul 21 '15 8:00pm

This message read