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CCSDTQ Optimized Geometry of Water Dimer.
1Department of Chemistry, University of Waikato , Private Bag 3105, Hamilton, New Zealand.
Journal of Chemical Theory and Computation
|November 22, 2015
Summary
Investigating the water dimer equilibrium geometry, this study used advanced coupled cluster theory. Including higher excitations beyond CCSD(T) showed smaller effects than core-valence correlation or relativistic factors.
Area of Science:
- Computational chemistry
- Quantum chemistry
- Molecular modeling
Background:
- The water dimer (H2O)2 is a fundamental model system for understanding hydrogen bonding.
- Accurate determination of its equilibrium geometry is crucial for theoretical chemistry.
Purpose of the Study:
- To investigate the equilibrium geometry of the lowest energy structure of the water dimer.
- To assess the impact of higher-order excitations in coupled cluster theory on the water dimer's geometry.
Main Methods:
- Coupled cluster theory, including singles, doubles, triples, and quadruples excitations (CCSDTQ).
- Optimization using the explicitly correlated coupled cluster singles doubles and perturbative triples [CCSD(T)-F12b] method.
- High-level ab initio electronic structure calculations.
Main Results:
- The equilibrium geometry was determined using a hierarchy of coupled cluster methods.
- The influence of excitations beyond coupled cluster singles doubles and triples [CCSD(T)] was found to be minor.
- The effect of higher excitations was comparable to core-valence correlation and relativistic effects.
Conclusions:
- Advanced coupled cluster methods, including CCSDTQ and CCSD(T)-F12b, provide accurate geometries for the water dimer.
- Core-valence correlation and relativistic effects are significant considerations for water dimer geometry.
- Higher-order excitations beyond CCSD(T) offer diminishing returns for this system.
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