Diffusion Monte Carlo evaluation of disiloxane linearisation barrier.

Area of Science:

• Quantum chemistry
• Computational chemistry
• Materials science

Background:

• Disiloxane, a silicate compound featuring the Si-O-Si bridge, presents theoretical challenges in predicting molecular properties.
• Accurate theoretical prediction of disiloxane properties is crucial for understanding silicate chemistry.

Purpose of the Study:

• To investigate the linearisation barrier of the disiloxane molecule.
• To evaluate the efficacy of the fixed-node diffusion Monte Carlo (FNDMC) method for predicting disiloxane properties.
• To compare FNDMC with Density Functional Theory (DFT) and Coupled Cluster (CCSD(T)) methods.

Main Methods:

• Fixed-node diffusion Monte Carlo (FNDMC) calculations were employed.
• Density Functional Theory (DFT) calculations were performed for comparison.
• Coupled Cluster method with single and double substitutions, including noniterative triples (CCSD(T)) calculations were conducted.

Main Results:

• FNDMC successfully predicted the linearisation barrier of disiloxane.
• FNDMC showed less dependence on basis-set completeness compared to DFT and CCSD(T).
• The study validates FNDMC as a reliable ab initio method for electronic correlation in disiloxane.

Conclusions:

• FNDMC is a suitable and accurate method for determining the linearisation barrier of disiloxane.
• The reliability of FNDMC in predicting disiloxane properties is established.
• FNDMC offers advantages over DFT and CCSD(T) regarding basis-set dependency.