Details

The conformational energy of hindered rotation in classical molecular mechanics simulation is approximated, in the general case, by the equation [1]:

.

The parameters and describe the force field, with torsion angle .

This Demonstration uses a modified version of the potential:

where is the energy barrier (kJ/mol); and are the energy difference gauche(-)/trans and gauche(+)/trans conformers, respectively.

To calculate the full distribution function at temperature , the Boltzmann distribution is used:

where is the universal gas constant, 8.314 J/mol K.

The mole fractions of the trans and gauche , conformers are calculated within ±10° relative to the local energy minima:

,

,

.

Reference

[1] M. Bachmann, Thermodynamics and Statistical Mechanics of Macromolecular Systems, Cambridge, UK: Cambridge University Press, 2014.