arXiv subjects

Abdulrahman Y. Zamani

Publications and source records attributed to Abdulrahman Y. Zamani.

3 recordsLinked to original sources

arXiv2026

Information-Theoretic Appraisal of Electron Densities

We present an information-theoretic assessment of atomic and molecular densities in the ground state and under a range of physical scenarios--excitation, confinement, and ensemblization. Comparisons across densities obtained from single-reference methods are facilitated through information entropy measures evaluated in position space. We demonstrate that the J-divergence serves as a key metric for benchmarking electron densities against coupled cluster and configuration interaction references. Mean-field orbital information is further compared with that of Brueckner and Dyson orbitals, and informational changes in multiple self-consistent-field solutions are examined under various symmetry-breaking conditions. We also explore the relationship between entropic measures of electron delocalization and the accuracy of the CO dipole moment computed with different methods. Our work offers insights into the selection of optimal reference determinants for a given chemical application and highlights potential benefits of incorporating information-entropy concepts in the development of new density functionals.

physics.chem-ph↗

arXiv2026

Kohn-Sham density encoding rescues coupled cluster theory for strongly correlated molecules

Coupled cluster theory with a Kohn-Sham reference (KS-CC) can dramatically outperform its Hartree-Fock counterpart for strongly correlated systems, but the origin of these improvements has remained unclear. Here we demonstrate that these improvements arise from differences in the one-particle density matrix that are encoded into the non-canonical Fock matrix and not from the nature of the KS orbitals, as is commonly assumed. Equipped with this insight, KS-CCSD(T) can be leveraged to achieve near-chemical-accuracy for electronic and thermochemical properties of transition-metal dimers and main-group compounds. Most strikingly, KS-CCSD(T) qualitatively recovers the entire Cr$_2$ potential energy surface, a notorious failure case for HF-CCSD(T) and single-reference density functional theory. We further introduce a density difference diagnostic that identifies multireference character and guides practitioners toward rational selections of optimal references at mean-field cost. These results establish KS-CCSD(T) as a practical route to treat strong correlation within the "gold standard" framework, and this has immediate implications for machine learning potential development and materials research, areas that heavily rely on KS-DFT for model-parameter fitting.

physics.chem-ph↗

arXiv2025

Towards ab initio Realizations of Collins' Conjecture

An ab initio approach formulated under an entropy-inspired repartitioning of the electronic Hamiltonian is presented. This ansatz produces orbital eigenvalues each shifted by entropic contributions expressed as subsets of scaled pair correlation energy terms present in second-order Moller-Plesset (MP) perturbation theory. Under the auspices of Collins' conjecture, which suggests that the electron correlation energy is approximately proportional to the Jaynes entropy of the one-electron density matrix, we introduce a parameter that controls the accuracy of the resultant one-electron density at the MP2 level. By tuning the density in a somewhat automated way, we achieve one-electron densities on par with those from full configuration interaction for single-bond dissociation. This parameter can then be used to add a Collins'-like static correlation correction to the energy functional, capturing both dynamical and nondynamical correlation effects in many-electron systems. The performance of the proposed method and its related variants approaches the accuracy of generalized valence bond theory for estimating single bond dissociation energies (BDEs) for set of small, closed-shell molecules composed of first and second row elements. Our results hold implications for reincorporating the missing (static) correlation energy in regularized perturbation theories that is typically discarded. Finally, we propose generic BDE parameters (accurate to within 7% on average) that could be used for strongly-correlated systems in general.

physics.chem-ph↗