Accelerating wavefunction in density-functional-theory embedding by truncating the active basis set.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Accurate wavefunction embedding in density-functional theory (DFT) is crucial for modeling complex chemical systems.
• Projector embedding simplifies these methods by ensuring orbital subspace orthogonality.
• Previous applications used the full atomic-orbital basis, limiting computational efficiency.

Purpose of the Study:

• To develop a more computationally efficient projector embedding method.
• To reduce the number of atomic orbitals required for correlated wavefunction calculations in the active subsystem.
• To achieve asymptotically size-independent computational cost for the active subsystem.

Main Methods:

• Truncation of the atomic-orbital basis set to include only functions near the active subsystem.
• Implementation of a projector operator to ensure orthogonality of orbital subspaces.
• Systematic investigation of accuracy controlled by a single parameter.

Main Results:

• The number of atomic orbitals becomes independent of the environment size, yielding O(N(0)) scaling for the active subsystem.
• Demonstrated applicability for calculating binding energies of water hexamers using embedded many-body expansion.
• Successfully computed reaction barriers for SN2 substitution reactions in α-fluoroalkanes.

Conclusions:

• The developed method significantly enhances computational efficiency for embedded quantum chemistry calculations.
• This approach allows for accurate and scalable simulations of chemical processes in complex environments.
• The controlled accuracy and efficiency make it suitable for various chemical applications, including solvation and reaction mechanisms.