Mridula Guin
mridula.guin@gmail.com
On Tue Jul 21 '15 8:00pm, Siddheshwar Chopra wrote
--------------------------------------------------
>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
>>>>>