arXiv subjects

Alexander V. Mironenko

Publications and source records attributed to Alexander V. Mironenko.

3 recordsLinked to original sources

arXiv2024

Analytical Correlation in the H$_{2}$ Molecule from the Independent Atom Ansatz

The independent atom ansatz of density functional theory yields an accurate analytical expression for dynamic correlation energy in the H$_{2}$ molecule: $E_{c} = 0.5(1 - \sqrt{2})(ab|ba)$ for the atom-additive self-consistent density $ρ= |a|^{2} + |b|^{2}$. Combined with exact atomic self-exchange, it recovers more than 99.5 % of nearly exact SCAN exchange-correlation energy at R > 0.5 $Å$, differing by less than 0.12 eV. The total energy functional correctly dissociates the H-H bond and yields absolute errors of 0.002 $Å$, 0.19 eV, and 13 cm$^{-1}$ relative to experiment at the tight binding computational cost. The chemical bond formation is attributed to the asymptotic Heitler-London resonance of quasi-orthogonal atomic states ($- (ab|ba)$) with no contributions from kinetic energy or charge accumulation in the bond.

physics.chem-ph↗

arXiv2024

Self-Consistent Equations for Nonempirical Tight Binding Theory

A new reference state for density functional theory, termed the independent atom ansatz, is introduced in this work. This ansatz allows for the exact representation of electron density in terms of non-interacting, atom-localized orbitals. Self-consistent equations for localized states are derived. Total energy functional is found to closely resemble tight binding theory. The independent atom ansatz facilitates partial cancellation of inter-atomic electron-electron and electron-nuclear interactions, which allows for the derivation of analytical Hamiltonian matrix elements in a weak interaction limit. The formalism provides charge and energy decomposition analyses at no additional cost. It also includes mechanisms to remove self-interaction and static correlation errors. Initial numerical results for simple model systems have been previously reported [Mironenko, J. Phys. Chem. A 127, 7836 (2023)].

physics.chem-ph↗

arXiv2020

Density Functional Theory-based Quantum Mechanics/Coarse-grained Molecular Mechanics: Theory and Implementation

Quantum mechanics/molecular mechanics (QM/MM) is a standard computational tool for describing chemical reactivity in systems with many degrees of freedom, including polymers, enzymes, and reacting molecules in complex solvents. However, QM/MM is less suitable for systems with complex MM dynamics due to associated long relaxation times, the high computational cost of QM energy evaluations, and expensive long-range electrostatics. Recently, a systematic coarse-graining of the MM part was proposed to overcome these QM/MM limitations in the form of the quantum mechanics/coarse-grained molecular mechanics (QM/CG-MM) approach. Herein, we recast QM/CG-MM in the density functional theory formalism and, by employing the force-matching variational principle, access the method performance for two model systems: QM CCl4 in the MM CCl4 liquid and the reaction of tert-butyl hypochlorite with the benzyl radical in the MM CCl4 solvent. We find that DFT-QM/CG-MM accurately reproduces DFT-QM/MM radial distribution functions and 3-body correlations between QM and CG-MM subsystems. The free energy profile of the reaction is also described well, with an error < 1-2 kcal/mol. DFT-QM/CG-MM is a general, systematic, and computationally efficient approach to include chemical reactivity in coarse-grained molecular models.

physics.chem-ph↗