[MMTK] scaling the amplitudes of the atomic displacement vectors

[Sergei Grudinin]

Dear MMTK users,

In module NormalModes the atomic displacement vectors are scaled acording to

amplitude=Numeric.sqrt(2.*temperature*Units.k_B/Units.amu) / 
(2.*Units.pi*self.frequencies[index])

Could you explain where factor 2 in 
Numeric.sqrt(2.*temperature*Units.k_B/Units.amu) is from?

Thanks in advance,

Sergei Grudinin.