Energy benchmarks for methane-water systems from quantum Monte Carlo and second-order Møller-Plesset calculations

Area of Science:

• Computational chemistry
• Quantum mechanics
• Materials science

Background:

• Accurate energy calculations are crucial for understanding molecular interactions.
• Methane-water clusters are relevant to hydrate formation and atmospheric chemistry.
• Quantum Monte Carlo (QMC) offers high accuracy but is computationally expensive.

Purpose of the Study:

• Generate accurate energy benchmarks for methane-water clusters using QMC.
• Assess the accuracy of the second-order Møller-Plesset (MP2) approximation for these clusters.
• Validate an embedded many-body technique for efficient MP2 calculations.

Main Methods:

• Utilized Quantum Monte Carlo (QMC) for high-accuracy energy benchmarks.
• Employed molecular dynamics simulations to obtain cluster geometries.
• Applied a recently developed embedded many-body technique for MP2 calculations.

Main Results:

• QMC benchmarks confirm the accuracy of coupled-cluster calculations for the methane-water dimer.
• MP2 approximation shows close agreement with QMC benchmarks for binding and cohesive energies.
• MP2 calculations, aided by the embedding technique, accurately predict energies for methane hydrate crystals.

Conclusions:

• The MP2 approximation, when corrected by an embedding approach, is reliable for large methane-water systems.
• QMC serves as a robust benchmark for validating lower-cost computational methods.
• Accurate energy benchmarks are essential for understanding the properties of methane-water clusters and hydrates.