Examining the Impact of Local Constraint Violations on Energy Computations in DFT.

This work examines the impact of locally imposed constraints in Density Functional Theory (DFT). Using a metric referred to as the extent of violation index (EVI), we quantify how well exchange-correlation functionals adhere to local constraints. Applying EVIs to a diverse set of molecules for GGA functionals reveals constraint violations, particularly for semi-empirical functionals.

Benchmarking DFT approximations for studying apatites.

Despite the growing interest in apatites, available experimental studies on their properties are limited in scope. Researchers, therefore, are increasingly resorting to predictions using density functional theory (DFT). However, large deviations can be seen between DFT-based estimates and experimental results, presumably due to approximations made in DFT models.

How Does HF-DFT Achieve Chemical Accuracy for Water Clusters?

Bolstered by recent calculations of exact functional-driven errors (FEs) and density-driven errors (DEs) of semilocal density functionals in the water dimer binding energy [Kanungo, B. 2024, 15, 323-328], we investigate approximate FEs and DEs in neutral water clusters containing up to 20 monomers, charged water clusters, and alkali- and halide-water clusters. Our proxy for the exact density is rSCAN 50, a 50% global hybrid of exact exchange with rSCAN, which may be less correct than rSCAN for the compact water monomer but importantly more correct for long-range electron transfers in the noncompact water clusters.

Unconventional Error Cancellation Explains the Success of Hartree-Fock Density Functional Theory for Barrier Heights.

Energy barriers, which control the rates of chemical reactions, are seriously underestimated by computationally efficient semilocal approximations for the exchange-correlation energy. The accuracy of a semilocal density functional approximation is strongly boosted for reaction barrier heights by evaluating that approximation non-self-consistently on Hartree-Fock electron densities, which has been known for ∼30 years. The conventional explanation is that the Hartree-Fock theory yields the more accurate density.

Pyrogallol-based dipodal optical probe as new smart analytical tool for sustainable detection of cobalt in biosystem.

The present research focuses on the micro-level detection of cobalt ions in biological and environmental samples using a new probe. The probe is a multifunctional symmetrical dipodal molecule with two pyrogallol binding units attached to the malonate scaffold through a propylene spacer. It was synthesized and characterized by H NMR, C NMR, IR, electronic spectroscopy, and mass spectrometry.