Momentum and velocity autocorrelation functions of a diatomic molecule are not necessarily proportional to each other.
We present a computation of the classical momentum and velocity correlation functions of Br2 considered as an idealized molecular wire connecting dissipated lead atoms at each end of the dimer. It is demonstrated that coupling of the diatomic relative momentum to the leads may result in momenta that are not equal to the mass-weighted velocity. These differences show up in numerical simulations of both the average value and time correlations of the bond momentum and velocity. These observations are supported by analytical predictions for the average temperature of the diatomic. They imply that the "standard recipes" for modeling the system with a generalized Langevin equation are insufficient.
Moix
Jeremy M
JM
Center for Computational Molecular Sciences & Technology, School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA.
Hernandez
Rigoberto
R
Pollak
Eli
E