Breakdown of equipartition of energy for vibrational heat capacity of diatomic molecular gas due to nonvanishing bond length

TL;DR

This paper investigates how considering the finite bond length in diatomic molecules causes deviations from the classical equipartition theorem in vibrational heat capacity calculations, especially near bond-breaking temperatures.

Contribution

It reveals the breakdown of equipartition of energy in vibrational modes due to non-zero bond length effects at high temperatures.

Findings

Significant deviation from standard vibrational heat capacity near bond-breaking temperatures.

The bond length influences the validity of the equipartition theorem in diatomic gases.

Breakdown of classical assumptions at high thermal energies.

Abstract

When the theorem of equipartition of energy applies to the vibrational degree of freedom within diatomic molecular gas, the bond length is usually taken as zero so that the theorem is valid. Once the bond length is taken into consideration, calculations show that the mean energy of the vibrational heat capacity will significantly deviate from the standard value near the high temperature which breaks down the bond.