radius of gyration,
A parameter characterizing the size of a particle of any shape. For a rigid particle
consisting of mass elements of mass
, each located at a distance
from the centre of mass, the radius of gyration,
, is defined as the square root of the mass-average of
for all the mass elements, i.e.
For a non-rigid particle, an average over all conformations is considered, i.e.
The subscript zero is used to indicate unperturbed dimensions, as in