First-principles simulation of molecular dissociation-recombination equilibrium.

Area of Science:

• Quantum chemistry
• Chemical physics
• Computational physics

Background:

• Accurate simulation of chemical reactions requires considering nuclear quantum effects and electron-nuclear coupling.
• Previous ab initio methods often neglect these dynamics, limiting their applicability at extreme temperatures.

Purpose of the Study:

• To perform the first first-principles simulation of chemical dissociation-recombination reactions.
• To consistently include nuclear quantum dynamics and nonadiabatic coupling.
• To investigate the H(3)(+) ion's behavior across a broad temperature spectrum.

Main Methods:

• Path integral Monte Carlo simulations were employed for full NVT quantum statistics.
• Ab initio quantum chemistry calculations were performed.
• Simulations covered temperatures from below room temperature to those relevant for planetary atmospheres.

Main Results:

• The study presents the equilibrium composition of dissociation-recombination reactions.
• Temperature and density-dependent reaction balance of the molecular ion and its fragments above 4000 K was determined.
• The density dependence of thermal ionization above 10,000 K was demonstrated.

Conclusions:

• This work provides a comprehensive, first-principles understanding of H(3)(+) ion chemistry.
• The inclusion of nuclear quantum effects and electron-nuclear coupling is crucial for accurate simulations.
• The findings are relevant for understanding planetary atmospheric physics.