ajjackson
commented
7 years ago This has now been implemented! The --mass_weighting option replaces --do_mass_weighting (a Boolean) with a real number. A value of zero leaves the scaling untouched; a value of +1 will add 1/sqrt(m) scaling to unscaled eigenvectors and a value of -1 will remove existing mass scaling. In-between values may be useful for adjusting relative movements to taste!
If you lose track of whether a system is weighted correctly, check the acoustic modes at the gamma-point. With correct mass-weighting, the atoms should move in unison.
I think the feature was requested by @aronwalsh?
The movement of light atoms such as hydrogen is much greater than that of heavier elements in modes that involve both atoms. While this is a physical effect, it can make it difficult to see coupling between atoms when the modes are visualised. An option to reduce the mass-weighting of phonon modes by rescaling the eigenvectors of lighter elements before normalisation would improve the legibility when illustrating systems such as hybrid organic-inorganic frameworks.