Electric Field Gradient Calculations for Ice VIII and IX Using Polarizable Embedding: A Comparative Study on...

Area of Science:

• Quantum computing
• Computational chemistry
• Solid-state physics

Background:

• Accurate computation of electric field gradients is essential for understanding molecular properties.
• Quantum computing offers a novel approach to complex chemical calculations.
• Previous methods like CASSCF have limitations in accuracy and computational cost.

Purpose of the Study:

• To assess the performance of the polarizable embedding variational quantum eigensolver self-consistent field (PE-VQE-SCF) model.
• To compare PE-VQE-SCF results with conventional complete active space self-consistent-field (CASSCF) calculations and experimental data.
• To investigate the impact of environmental inclusion on computational accuracy.

Main Methods:

• Utilized the PE-VQE-SCF model, based on an adaptive derivative-assembled problem-tailored (ADAPT) ansatz.
• Computed quadrupole coupling constants for ice VIII and ice IX.
• Compared quantum-computing results with classical PE-CASSCF and experimental measurements.

Main Results:

• PE-VQE-SCF results closely agreed with classical PE-CASSCF calculations and experimental findings.
• Inclusion of the environment was critical for matching experimental data.
• Calculations for ice VIII were within experimental uncertainty for both CASSCF and VQE-SCF.
• The VQE-SCF model showed that environmental inclusion complicates the wavefunction and optimization, potentially increasing circuit depth.

Conclusions:

• The PE-VQE-SCF model demonstrates high accuracy for electric field gradient calculations.
• Environmental effects are crucial for achieving experimental agreement in quantum chemical simulations.
• Quantum computing holds promise for advancing computational chemistry, though circuit complexity needs consideration.