An Orthogonal Electronic State View on Charge Delocalization and Transfer.

Area of Science:

• Quantum chemistry
• Computational chemistry
• Chemical physics

Background:

• Configuration interaction (CI) is a quantum chemical method.
• Understanding electron distribution and charge transfer is key in chemical bonding and reactions.
• The nature of the hydrogen bond in water dimer has been debated.

Purpose of the Study:

• To present a novel configuration interaction (CI) framework using charge-localized determinants.
• To provide a clear interpretation of adiabatic states as resonance hybrids.
• To define electronic coupling for electron transfer processes and analyze the water dimer hydrogen bond.

Main Methods:

• Expressing the electronic Hamiltonian in a basis of charge-localized determinants.
• Independently generating adiabatic CI states and charge-localized CI states via diagonalization.
• Analyzing the water dimer hydrogen bond using the developed CI framework.

Main Results:

• The CI framework offers a straightforward interpretation of adiabatic states as resonance hybrids.
• Charge-localized states provide a clear definition of electronic coupling for electron transfer.
• Analysis of the water dimer reveals small overall charge transfer but highlights the importance of ionic contributions for accurate potential energy surfaces.

Conclusions:

• The presented CI framework effectively describes charge delocalization and electron transfer.
• Ionic contributions, though small in magnitude, are critical for accurately modeling the water dimer's potential energy surface.
• This approach provides valuable insights into chemical bonding and intermolecular interactions.