Author Topic: too many negative wave numbers  (Read 5034 times)

ekirillov

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too many negative wave numbers
« on: November 12, 2009, 03:47:13 PM »
Hello,

I'm running calculation on the series of cationic species of Zr (generally, of the formula [Cp2Zr-Me]+ with ca. 120 atoms). After successful optimization BP86-RI/ SVP (C,H) TZVPP (Zr) with moderate accuracy (SCF: m3 grid, conv 10(-7)), I have run aoforce. It afforded  25 modes with ********** frequency value and 221 modes with wave numbers in between -980842.77 and -6513.93 cm-1, 3 modes with frequences from  -0.03 to -0.01. The other 61 modes are positive.
I'm a bit confused by having this result. This would be a saddle point of the 249th order ??? How this data might be rationally interpreted then ?

Thanks
« Last Edit: November 12, 2009, 03:54:04 PM by ekirillov »

uwe

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Re: too many negative wave numbers
« Reply #1 on: November 13, 2009, 10:10:27 AM »
Hello,

a few negative numbers can occur if you are starting from a symmetric structure which represents a saddle point of higher order. But 249 is really a bit too high :-) - even if you have used a symmetric structure.

It could be a technical issue like problems with I/O, etc. But then a simple restart of aoforce should give reasonable numbers.

Another possibility to check if the vibrational modes are reasonable or not is to open the control file in TmoleX and visualize the vibrations (or any other visualizer after using tm2molden for molden input file or 'screwer -vibro' for multi-xyz file or aoforce2g98 for G98 type input files).

If all that does not help: Write an email to the Turbomole Support!!

Regards,

Uwe