Dear Rajamani Akilan thank you for posting this interesting technical question. In this context please have a look at the following potentially useful links which might help you in your analysis:

Extract principal components

https://www.geo.fu-berlin.de/en/v/soga/Geodata-analysis/Principal-Component-Analysis/principal-components-basics/Extract-principal-components/index.html

The eigenvectors of Gaussian matrices with an external source

Article The eigenvectors of Gaussian matrices with an external source

This article has been posted by the authors as public full text on RG, so it can be freely downloaded as pdf file.

For a definition of Hessian and eigenvectors please go through the following helpful link:

Hessian, Eigenvalues, Eigenvectors, and Stability in the Surface Evolver

http://facstaff.susqu.edu/brakke/evolver/workshop/doc/eigentut.htm

I hope this helps. Good luck with your research and best wishes, Frank Edelmann

Dear Prof. Frank T. Edelmann and Dear Prof. P. Contreras,

Thank you for your links.

@Prof.P. Contreras , Now understand that the Hessian comes under the “Cartesian force constant” in (G16/09) FCHK file. But I need eigenvectors for my calculations. Will it be written in G16 log/fchk file? If the statement is true, where do I have to look for the eigenvectors in G16 output files?

Thanks in advance