ABSTRACT
Recent regularization of the SCAN meta-GGA functional (rSCAN) has simplified the numerical complexities of the SCAN functional, alleviating SCAN's stringent demand on the numerical integration grids to some extent. The regularization of rSCAN, however, results in the breaking of some constraints such as the uniform electron gas limit, the slowly varying density limit, and coordinate scaling of the iso-orbital indicator. Here, we assess the effects of regularization on the electronic, structural, vibrational, and magnetic properties of molecules by comparing the SCAN and rSCAN predictions. The properties studied include atomic energies, atomization energies, ionization potentials, electron affinities, barrier heights, infrared intensities, dissociation and reaction energies, spin moments of molecular magnets, and isomer ordering of water clusters. Our results show that rSCAN requires less dense numerical grids and gives very similar results to those of SCAN for all properties examined with the exception of atomization energies, which are worsened in rSCAN. We also examine the performance of self-interaction-corrected (SIC) rSCAN with respect to SIC-SCAN using the Perdew-Zunger (PZ) SIC method. The PZSIC method uses orbital densities to compute one-electron self-interaction errors and places an even more stringent demand on numerical grids. Our results show that SIC-rSCAN gives marginally better performance than SIC-SCAN for almost all properties studied in this work with numerical grids that are on average half or less as dense as that needed for SIC-SCAN.
ABSTRACT
A chemiresistor sensor for ultra-low levels of elemental mercury (Hg0) vapor is described. The sensor was prepared through thermal reduction of graphene oxide (GO) deposited on an interdigitated electrode using only low temperature annealing typically at 230 °C. The sensor responds to the presence of Hg0 vapor within <1 min and spontaneously recovers its baseline through flushing with a Hg0-free carrier gas. The sensor has a linear response in the range of 0.5 to 12.2 ppbv of Hg0 vapor and a detection limit of 0.10 ppbv. The amount of GO and annealing temperature affect the sensor response and were optimized. The sensor can find use in monitoring exposure of persons to Hg0 vapors, for which a threshold value of 6.1 ppbv has been set by the World Health Organization. Graphical abstract Schematic of an interdigitated electrode modified with a layer of thermally reduced graphene oxide. It can be used as a chemiresistive sensor for Hg0 vapor. The sensor displays a rapid and reversible response and has an ultralow detection limit of 0.10 ppbv.
