what is the unit for IR intensity using normal mode analysis in cp2k?

[fyya...@gmail.com]

Hi, all,

What is the unit for IR intensity using normal mode analysis in cp2k? The IR intensity is proportional to d(mu) / dQ, d(mu) is the change of the dipole moment, and dQ is the change of normal mode coordinate Q. 

There are prefactor for the exact IR intensity,  see eq. 8 in Cynthia L. Darling and H. Bernhard Schlegel, J. Phys. Chem. 1994, 98, 5855-5861. 

So what is the equation for calculating the IR intensity in cp2k, is there a reference for it? Once we know the equation, we can know the unit. 

Thanks!

Fangyong