Microcanonical Rate Constants With Rice-Ramsperger-Kassel-Marcus in Eyringpy.

Rice-Ramsperger-Kassel-Marcus (RRKM) theory was implemented in Eyringpy to enable the computation of microcanonical rate constants, densities of states (DOS), and sums of states. Input can be provided either as experimental data or directly from electronic-structure output files, requiring minimal user specification. The Stein-Rabinovitch algorithm was employed for accurate state counting, and tunneling corrections were introduced through the Eckart model to account for light-particle transfer and narrow barriers. To validate the implementation, the DOS of hydrogen peroxide was evaluated with anharmonic-vibrational corrections, and three gas-phase reactions were analyzed: thermal decomposition of digermane, bromine-atom loss from CH2BrO·, and hydrofluoric-acid elimination from CF3CH3. The validation confirms that Eyringpy provides accurate and efficient RRKM calculations, providing reliable kinetic analyses of unimolecular reactions across a broad energy range.