Thermodynamics of the rupture in a Morse lattice

The rupture of a Morse lattice is considered in the present paper. The critical rupture force Fcr is found to decrease with the number of particles N as Fcr ~ 1/$\sqrt{N}$. The partition function is obtained for two states of the lattice – with all equal bond lengths and one broken bond. In the first case an accurate expressions for thermodynamic parameters are obtained, and thermodynamic expressions are derived in the harmonic approximation in the latter case. The analytical predictions are confirmed by extensive MD simulations. Cis-trans isomerization is considered as an example. Volume fractions of trans- and cis-isomers versus number of monomer units N are found depending on the torsion stiffnesses