Projected-interacting full configuration interaction plus regularized perturbation theory: DFT-inspired wavefunction
1Department of Chemistry and Biochemistry, Texas Christian University, 2800 S. University Dr., Fort Worth, Texas 7629, USA.
The Journal of Chemical Physics
|August 3, 2026
Summary
Projected-interacting full configuration interaction (PiFCI) offers a way to simulate complex molecular quantum devices. This method accurately captures electron correlation in large systems, crucial for computational chemistry.
Area of Science:
- Quantum chemistry
- Computational materials science
- Molecular quantum devices
Background:
- Accurate quantum simulations are essential for designing molecular quantum devices.
- Existing methods struggle with large numbers of entangled or strongly correlated electrons.
- Chemical accuracy is needed for reliable computational design.
Purpose of the Study:
- To present a general treatment of projected interactions in Projected-interacting full configuration interaction (PiFCI).
- To introduce regularized second-order many-body perturbation theory (MP2) as an approximate projected exchange-correlation (XC) functional for PiFCI.
- To demonstrate the accuracy of PiFCI with regularized MP2 for modeling molecular quantum devices.
Main Methods:
- Developed a general treatment for projected interactions within the PiFCI framework.
- Introduced regularized MP2 as a novel approximate projected XC functional.
- Applied PiFCI with regularized MP2 to model entangled organic radicals (tetrathiafulvalene and phenalenyl).
Main Results:
- PiFCI with regularized MP2 accurately treats both dynamical and nondynamical electron correlation.
- The method performs well in relatively large active spaces.
- Successful modeling of molecular quantum device components like entangled tetrathiafulvalene and phenalenyl radicals.
Conclusions:
- PiFCI combined with regularized MP2 is a promising method for accurate quantum chemical simulations.
- This approach advances the computational design of molecular quantum devices.
- The method effectively handles complex electron correlation in challenging molecular systems.
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