The structure factor, , for a monatomic system is defined by:
where is the scattering wave-vector modulus
At zero wavenumber, i.e. ,
from which one can calculate the isothermal compressibility.
To calculate in molecular simulations one typically uses:
where is the number of particles and and are the coordinates of particles and respectively.
The dynamic, time dependent structure factor is defined as follows:
The ratio between the dynamic and the static structure factor, , is known as the collective (or coherent) intermediate scattering function.
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