Molecular multibond dissociation with small complete active space augmented by correlation density functionals.

Area of Science:

• Quantum chemistry
• Computational chemistry
• Theoretical chemistry

Background:

• Molecular multibond dissociation presents significant challenges for theoretical chemistry due to complex electron correlation effects.
• Accurate theoretical descriptions are crucial for understanding chemical reactions and molecular properties.

Purpose of the Study:

• To develop an efficient and accurate computational method for describing molecular multibond dissociation.
• To incorporate long-range and short-range electron correlation effects in a unified approach.

Main Methods:

• The proposed Complete Active Space Π(M) Density Functional Theory (CASΠ(M)DFT) method combines Complete Active Space Self-Consistent Field (CASSCF) with Density Functional Theory (DFT).
• CASSCF handles nondynamic correlation in stretched bonds, while DFT functionals (modified Lee-Yang-Parr) address dynamic correlation.
• A small active space is used to capture essential correlation effects efficiently.

Main Results:

• CASΠ(M)DFT accurately reproduces benchmark potential energy curves (PECs) for multibonded molecules (N2, CO, H2O, C2).
• Calculations were performed using a modest triple-zeta basis set, demonstrating computational efficiency.
• The method effectively captures both nondynamic and dynamic electron correlation effects.

Conclusions:

• CASΠ(M)DFT offers a computationally efficient and accurate approach for studying molecular dissociation.
• This method provides a reliable tool for theoretical investigations of complex chemical systems involving multibond dissociation.