What is it about?
This work extends the optimized effective potential (OEP) method, traditionally used for band gap evaluations and benchmarks, to analytically calculate atomic forces in molecular and solid systems within the pseudopotential and plane-wave framework. A new contribution to the Hellmann-Feynman forces, accounting for the electronic exchange-correlation effects, is derived to handle the use of nonlocal pseudopotentials. Calculating this extra OEP force term for the Hartree-Fock and hybrid PBE0 functionals yield forces with excellent numerical accuracy, enabling precise determination of equilibrium geometries and vibrational frequencies.
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Why is it important?
Evaluating atomic forces within the Optimized Effective Potential (OEP) method is of importance for the advanced methods that utilize this approach. This includes some based on the Random Phase Approximation (RPA) framework. This work therefore represents an essential first step in extending force calculations to these advanced methods.
Perspectives
Atomic forces, which correspond to the gradient of the energy with respect to atomic displacements, are crucial quantities for determining the equilibrium geometry of molecular and solid systems and for computing vibrational frequencies. Certain systems, such as high-pressure molecular solid hydrogen phases under megabar pressure conditions, prove highly sensitive to the level of description of the energy, making essential an accurate evaluation of the energies and forces. This study paves the way for extending force calculations to the advanced Random Phase Approximation methods based on the OEP, offering the potential for more reliable results on these sensitive systems.
Mr. Damian Contant
Universite Paris-Sorbonne
Read the Original
This page is a summary of: Optimized effective potential forces with the plane-wave and pseudopotential method, September 2024, American Physical Society (APS),
DOI: 10.1103/physrevb.110.125110.
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