Dear Yugo Hirade

1 AU = 2.541765 D

So, to convert an electric dipole moment from AU to Debye, you would simply multiply the value in au by 2.541765. For example, if the electric dipole moment in au is 1.0, then the electric dipole moment in Debye would be 2.541765 D.

The unit of transition electronic dipole moment in Time-Dependent Density Functional Theory (TD-DFT) calculations using Gaussian software is typically reported in Debye (D) units.

Debye (D) is a common unit used to measure electric dipole moments. When performing TD-DFT calculations in Gaussian, the transition electronic dipole moment is often reported in Debye units to represent the magnitude and direction of the transition between electronic states.

Hope this will help you, thanks and regard

Thank you for your reply.

I had assumed that 'AU' was an arbitrary unit.

Your point confirms that 'AU' is an atomic unit.

Thank you very much.