Units

Internally dynasor uses units of Ångström (Å) for length, femtosecond (fs) for time, and electronvolt (eV) for energy. This means that all calculated correlation functions will be in terms of these units.

Note that \(\boldsymbol{q}\)-points are defined to include the factor \(2\pi\) as is commonly done in physics (wavenumber wikipedia). This means that \(\boldsymbol{q}\)-points technically have units of rad/Å, but note that this in the literature is usually simply written as 1/Å. This is how the units of dynasor are reported in the first dynasor paper (see credits page), but as leaving out the explicit mention of rad leads to ambiguity, we have since then begun to explicitly include rad when reporting \(\boldsymbol{q}\)-point units. Therefore, you will throughout the examples in the documentation encounter rad/Å.

To further clarify the inclusion of the factor \(2\pi\) in \(\boldsymbol{q}\), note that \(\boldsymbol{q}\) arises in a spatial Fourier transform, which means that it can be compared to a temporal Fourier transform. A temporal Fourier transform can be written in terms of the frequency \(f\) (with units 1/s), in which case the exponential explicitly contains a factor of \(2\pi\), or in terms of angular frequency \(\omega=2\pi f\) (with units rad/s). When performing the spatial Fourier transform here, the exponential does not contain an explicit factor of \(2\pi\), meaning that \(\boldsymbol{q}\) must be interpreted as the spatial analogue of the angular frequency \(\omega,\) thus containing a factor of \(2\pi\) and having the unit rad/Å.