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update mass unit to CODATA 2010 value #443

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update mass unit to CODATA 2010 value #443

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c157f83
update mass unit to CODATA 2010 value
orbeckst Sep 3, 2026
f7406f7
fix whitespace
orbeckst Sep 3, 2026
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12 changes: 11 additions & 1 deletion doc/source/units.rst
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Expand Up @@ -28,10 +28,20 @@ Other base units are listed in the table :ref:`table-baseunits`.
charge :math:`e` :math:`1.602176565 \times 10^{-19}` As
force kJ/(mol路脜) :math:`1.66053892103219 \times 10^{-11}` J/m
speed 脜/ps :math:`100` m/s
mass u :math:`1.66053906660(50) \times 10^{-27}` kg
mass u :math:`1.66053892103219 \times 10^{-27}` kg
angle degrees :math:`\frac{\pi}{180}` rad
=========== ============== ===============================================

MDAnalysis units are currently based on the NIST `CODATA 2010`_ values for
physical constants. The unit of mass is not explicitly used but implicit in the
units for force and energy via Avogadro's constant :math:`6.02214129(27) \times
10^{23}\,\mathrm{mol}^{-1}` (in :data:`MDAnalysis.units.constants`). The excess
precision in the table is due to the use of the inverse of Avogadro's constant
and listing all available digits of the numerical calculation.

.. _`CODATA 2010`:
https://physics.nist.gov/cuu/Constants/ArchiveASCII/allascii_2010.txt


Unit conversion
===============
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