Eunji Sim

Density functional theory (DFT) calculations have become widespread in both chemistry and materials, because they usually provide useful accuracy at much lower computational cost than wavefunction-based methods. All practical DFT calculations require an approximation to the unknown exchange-correlation energy, which is then used self-consistently in the Kohn-Sham scheme to produce an approximate energy from an approximate density. Density-corrected DFT is simply the study of the relative contrib

We argue that any general mathematical measure of density error, no matter how reasonable, is too arbitrary to be of universal use. However, the energy functional itself provides a universal relevant measure of density errors. For the self-consistent density of any Kohn-Sham calculation with an approximate functional, the theory of density-corrected density functional theory (DC-DFT) provides an accurate, practical estimate of this ideal measure. We show how to estimate the significance of the d

All-electron fixed-node diffusion Monte Carlo provides benchmark spin gaps for four Fe(II) octahedral complexes. Standard quantum chemical methods (semilocal DFT and CCSD(T)) fail badly for the energy difference between their high- and low-spin states. Density-corrected DFT is both significantly more accurate and reliable and yields a consistent prediction for the Fe-Porphyrin complex.

Density-corrected DFT is a method that cures several failures of self-consistent semilocal DFT calculations by using a more accurate density instead. A novel procedure employs the Hartree-Fock density to bonds that are more severely stretched than ever before. This substantially increases the range of accurate potential energy surfaces obtainable from semilocal DFT for many heteronuclear molecules. We show that this works for both neutral and charged molecules. We explain why and explore more di

An on-the-fly filtered propagator functional path integral scheme is introduced as an efficient way of calculating the iterative dynamics of complex condensed systems. Time evolution of the reduced density matrix of a dissipative quantum system is evaluated iteratively by filtering the negligible propagator elements at each propagation step. This on-the-fly filtering along with the finiteness of the bath memory dramatically reduces the configuration space to be integrated without losing numerica

Recently, various energy transducers driven by the relative motion of solids and liquids have been demonstrated. However, in relation to the energy transducer, a proper understanding of the dynamic behavior of ions remains unclear. Moreover, the energy density is low for practical usage mainly due to structural limitations, a lack of material development stemming from the currently poor understanding of the mechanisms, and the intermittently generated electricity given the characteristics of the

We present accurate path integral simulations of the primary charge separation in bacterial photosynthesis. The process is modeled in terms of the three coupled electronic states corresponding to the photoexcited special pair (the electron donor), the reduced accessory bacteriochlorophyll (the bridge), and the reduced bacteriopheophytin (the primary electron acceptor) of the L branch which interact with a dissipative medium of protein and solvent degrees of freedom. The electronic state populati

Oligoindole-based chiral foldamers have been synthesized by incorporating (S)- or (R)-1-phenylethylamine to both ends of the tetraindole scaffold. The oligoindoles fold into a helical conformation upon binding an anion by hydrogen bonds, which gives rise to an induced circular dichroism (CD) signal of large amplitude, implying the preferential formation of one helical isomer over another. Theoretical calculations suggest that the (P)-helix of the (S,S)-oligoindole 8a be more energetically stable

Dispersion corrections of various kinds usually improve DFT energetics of weak noncovalent interactions. However, in some cases involving molecules or halides, especially those with σ-hole interactions, the density-driven errors of uncorrected DFT are larger than the dispersion corrections. In these abnormal situations, HF-DFT (using Hartree-Fock densities instead of self-consistent densities) greatly improves bond energies, while dispersion corrections can even worsen the results. On the other

The development of energy-conversion devices using water movement has actively progressed. Ionovoltaic devices, which are driven by ion dynamics, show ion specificity by which different ions with identical charges show different output performance. However, the ion specificity remains poorly understood because the influence of the ion species on generated electric signals is not elucidated. The ion specificity in electric signals induced by flowing water droplet was investigated in terms of its

Empirical fitting of parameters in approximate density functionals is common. Such fits conflate errors in the self-consistent density with errors in the energy functional, but density-corrected DFT (DC-DFT) separates these two. We illustrate with catastrophic failures of a toy functional applied to H₂⁺ at varying bond lengths, where the standard fitting procedure misses the exact functional; Grimme's D3 fit to noncovalent interactions, which can be contaminated by large de

Abstract Heterometal doping is a powerful method for tuning the physicochemical properties of metal nanoclusters. While the heterometals doped into such nanoclusters predominantly include transition metals with closed d‐shells, the doping of open d‐shell metals remains largely unexplored. Herein, we report the first synthesis of a [RhHAg 24 (SPhMe 2 ) 18 ] 2− nanocluster, in which a Rh atom with open d‐shells ([Kr]4d 8 5s 1 ) is incorporated into the Ag 24 framework by forming a RhH superatom wi

Kohn-Sham (KS) inversion, that is, the finding of the exact KS potential for a given density, is difficult in localized basis sets. We study the precision and reliability of several inversion schemes, finding estimates of density-driven errors at a useful level of accuracy. In typical cases of substantial density-driven errors, Hartree-Fock density functional theory (HF-DFT) is almost as accurate as DFT evaluated on CCSD(T) densities. A simple approximation in practical HF-DFT also makes errors