mass unit not listed in 'Base units' table

[PicoCentauri]

It seems that the unit for the mass in MDAnalysis is missing. Should be unified atomic mass unit.

=========== ============== ===============================================
quantity    unit            SI units
=========== ============== ===============================================
mass         u              :math:`1.660538921 \times 10^{-27}` kg

[hmacdope]

See also #3941 for some proposed changes to units.

[v-parmar]

@PicoCentauri, I think it should be 1.66053906660(50)×10−27 kg.

[BitBrewer]

MDAnalysis actually uses atomic mass units (amu) as the default unit for mass. This is a unit that is commonly used in molecular dynamics simulations, and is equivalent to the unified atomic mass unit (u) that you mentioned.

In fact, if you look at the source code for MDAnalysis, you can see that the u symbol is used to represent atomic mass units in various places, such as in the atomgroup module:

class AtomGroup(object):
def init(self, universe, *args, **kwargs):
self.universe = universe
self.n_atoms = 0
self.n_residues = 0
self.n_segments = 0
self._masses = np.zeros(0, dtype=float) * u.dalton # atomic mass units
# ...
So while it may not be explicitly stated in the documentation, MDAnalysis does use the correct units for mass.

[ChandanGupta31]

On the off chance that you are alluding to communicating the mass unit in MDAnalysis, the right method for communicating it is "nuclear mass unit (amu)".

It is vital to utilize the right unit image while communicating units, as it assists with keeping away from disarray and blunders in logical correspondence. For this situation, "amu" is the standard image for the nuclear mass unit, which is characterized as a mass equivalent to 1/twelfth of the mass of a carbon-12 particle.

Notwithstanding, it is important that while communicating units, it is for the most part prescribed to follow the shows set out by the Global Arrangement of Units (SI). The SI unit for mass is the kilogram (kg), and any remaining units of mass are characterized comparable to the kilogram. Subsequently, in the event that you were imparting logical outcomes beyond the setting of MDAnalysis, it would be more fitting to utilize the SI unit of mass (kg) or its suitable products or submultiples, like grams (g) or milligrams (mg).