The phonon spectrum

[bubble]

Hi,
   Recently, I want to calculate the phonon sprectrum of 2D boron sheet. The experiment has shown that this system is stable. But I found negative frequencies at PBE/DZP level. I wonder whether the theoretical level that I considered is too low? Any suggestion?

Thank you!

[Ulrik G. Vej-Hansen]

A common mistake is that the geometry is not optimized well enough, so have you made sure of that?

The accuracy of phonon calculations can be very sensitive to the details of the calculation, so it might be that that particular basis set is not optimal for phonon calculations of 2D Boron. See also our tutorial category on phonons and thermal transport: http://docs.quantumwise.com/tutorials/phonons_thermal.html