Combining Density Functional Embedding Theory and DMRG-NEVPT2 to Treat Large Active Spaces: Addressing Electronic...

Area of Science:

• Computational chemistry
• Materials science
• Surface science

Background:

• Single-atom alloys (SAAs) are crucial in heterogeneous catalysis due to unique electronic properties.
• Density functional theory (DFT) is widely used but has limitations for photo- and electrocatalysis.
• Density functional embedding theory (DFET)/embedded correlated wavefunction (ECW) methods can correct DFT errors.

Purpose of the Study:

• To develop and apply advanced computational methods for accurate modeling of SAAs.
• To overcome limitations of traditional multireference methods for SAAs with complex electronic structures.
• To investigate CO adsorption on various metal-doped Ag(100) surfaces.

Main Methods:

• Combined DFET/ECW with density matrix renormalization group (DMRG) methods (DMRGSCF and DMRG-NEVPT2) within the PySCF code.
• Utilized embedded DMRGSCF and embedded DMRG-NEVPT2 for calculations.
• Analyzed CO adsorption on Ni-, Rh-, Pd-, and Pt-doped Ag(100) using varying active spaces.

Main Results:

• Conventional active spaces in multireference methods led to overbinding of CO.
• Larger active spaces, enabled by DMRGSCF and DMRG-NEVPT2, provided accurate adsorption free energies.
• The choice of active space significantly impacts the accuracy of calculated adsorption energies.

Conclusions:

• Embedded DMRG-NEVPT2 is a powerful method for studying catalytic reactions on metal surfaces, especially when large active spaces are needed.
• Future multireference calculations for SAAs should include all dopant d-orbitals and relevant host metal orbitals.
• This work provides a reliable computational framework for understanding SAA catalysis.