Recent Advances in Cartesian-Grid DFT in Atoms and Molecules.

In the past several decades, density functional theory (DFT) has evolved as a leading player across a dazzling variety of fields, from organic chemistry to condensed matter physics. The simple conceptual framework and computational elegance are the underlying driver for this. This article reviews some of the recent developments that have taken place in our laboratory in the past 5 years. Efforts are made to validate a viable alternative for DFT calculations for small to medium systems through a Cartesian coordinate grid- (CCG-) based pseudopotential Kohn-Sham (KS) DFT framework using LCAO-MO ansatz. In order to legitimize its suitability and efficacy, at first, electric response properties, such as dipole moment ( µ ), static dipole polarizability ( α ), and first hyperpolarizability ( ß ), are calculated. Next, we present a purely numerical approach in CCG for proficient computation of exact exchange density contribution in certain types of orbital-dependent density functionals. A Fourier convolution theorem combined with a range-separated Coulomb interaction kernel is invoked. This takes motivation from a semi-numerical algorithm, where the rate-deciding factor is the evaluation of electrostatic potential. Its success further leads to a systematic self-consistent approach from first principles, which is desirable in the development of optimally tuned range-separated hybrid and hyper functionals. Next, we discuss a simple, alternative time-independent DFT procedure, for computation of single-particle excitation energies, by means of "adiabatic connection theorem" and virial theorem. Optical gaps in organic chromophores, dyes, linear/non-linear PAHs, and charge transfer complexes are faithfully reproduced. In short, CCG-DFT is shown to be a successful route for various practical applications in electronic systems.

The use of algae for environmental sustainability: trends and future prospects.

Algae are photosynthetic prokaryotic or eukaryotic ubiquitously found group of organisms. Their enormous potentiality in coping up with various environmental crises has been well documented. Algae have proven to be ideal for biomonitoring of water pollution and help in removing the pollutants with their process of bioremediation apart from the production of eco-friendly sources of energy. Industries like food and pharmaceuticals are exploiting algae for producing several value-added products. The agricultural sector is also highly benefited from microalgae, as they are the good promoters of crop growth. The CO2-removing potential of algae proves to be an asset in fighting climate change. Moreover, the relatively easy and inexpensive methods of sampling and culturing of algae make them more popular. In this paper, we review the sustainable application aspects of algae in various areas like pollution control, energy production, agriculture, and fighting climate change. Critical discussions have been made on the recent trends and advances of algal technologies indicating future prospects.

Charge-Transfer Excitation within a Hybrid-(G)KS Framework through Cartesian Grid DFT.

Organic molecules that exhibit charge-transfer (CT) excited states are known to play an important role in processes linked to electron transfer properties and molecular conductance. In this article, we present a simple technique based on "Becke's excitation theorem" that offers an accurate picture of these electronic states. It expresses the correlated energy splitting between triplet and its corresponding singlet states by a two-electron integral, which is numerically evaluated by our recently developed strategy on Cartesian grid. We first examine the consistency of our adopted numerical strategy to evaluate the integral with the original prescribed technique. Then we assess the method on weakly bound CT complexes with three different functionals (BLYP, B3LYP, and LC-BLYP). The accuracy on asymptotic limit of CT excitation is also explored. Finally in order to illustrate the strength and feasibility, it is further extended to a few "challenging" molecules. The method, when employed with hybrid B3LYP functional, turns out to be quite accurate to describe CT excitation energy.

Presentation, Diagnostic Dilemma, and a Novel Approach of Fixing a Cedell's Fracture - A Case Report.

Introduction: Fractures of the posteromedial tubercle of talus are one of the rarer fractures encountered in clinical practice. They mostly present like an ankle sprain which often leads to missed injuries and delayed diagnosis. We present one such case, incorporating the dilemmas associated with its diagnosis, treatment, approach to the treatment and a novel way of fixation and the outcome. Not much of literature has been published in this regard. Case Presentation: A 38-year-old Indian military man presented with pain and swelling over posteromedial aspect of his right ankle for 7 days, following an awkward landing during one of his training drills. He was unable to bear weight on the affected limb. On examination, passive flexor hallucis longus tendon movement was painful. A 30° external rotation lateral view radiograph of the ankle showed a hypolucent shadow posterior to the posterior talar process. An avulsion fracture of the posteromedial tubercle of talus was confirmed on computed tomography scan. Internal fixation for the fracture was done by a novel mini open technique and a strict rehabilitation protocol was followed. Twelve weeks postoperatively, he was allowed to resume his work and X-ray confirmed complete bony union. The patient at 6 months follow-up did well with full range of ankle motion. Conclusion: First, a high clinical suspicion and vigilance are required for the diagnosis of a Cedell's fracture. Missing such injuries could lead to varied morbidities. There is no blanket treatment protocol for such fractures. The ideal treatment should be customized as per the fracture morphology; and internal fixation is one of the options. The mini open technique is a viable approach to fix such fractures.

A Simple Effective Δ SCF Method for Computing Optical Gaps in Organic Chromophores.

Photoluminescence effects in organic chromophores are of significant importance and requires precise description of low lying excited states. In this communication, we put forward an alternative time-independent DFT scheme for computing lowest single-particle excitation energy, especially for singlet excited state. This adopts a recently developed "virial"-theorem based model of singlet-triplet splitting which requires a DFT calculation on closed shell ground state and a restricted open-shell triplet excited state, followed by a simple 2 e - integral evaluation. This produces vertical excitation energies in small molecules, linear and non-linear polycyclic aromatic hydrocarbon and organic dyes in comparable accuracy to the TDDFT. We also explore the functional dependency of present method with three different functionals (B3LYP, wB97X and CAM-B3LYP) for polyenes and linear acenes. A systematic comparison with literature value illustrates the validity and usefulness of the present scheme in determining optical gap with fair computational cost.

Practical Aqueous Calcium-Ion Battery Full-Cells for Future Stationary Storage.

There is a pressing need for high-rate cycling and cost-effective stationary energy storage systems in concomitance with the fast development of solar, wind, and other types of renewable sources of energy. Aqueous rechargeable Ca-ion batteries have the potential to meet the growing demands of stationary energy storage devices because they are abundant and safe; they can also be manufactured at a low-cost and have a higher volumetric capacity. In this study, we have demonstrated a low-cost, safe, aqueous Ca-ion battery that is based on a low potential, lower specific weight, in situ polymerized polyaniline as an anode, and a high redox-potential open-framework structured potassium copper hexacyanoferrate as a cathode. The charge-discharge mechanism of this battery includes doping/dedoping of NO3- at the anode, and intercalation and deintercalation of Ca-ion at the cathode. This Ca-ion battery works successfully in a 2.5 M Ca(NO3)2 aqueous electrolyte that exhibits 70 Wh kg-1 specific energy at 250 W kg-1 and even maintains a high energy density of 53 Wh kg-1 at a higher rate of 950 W kg-1; this indicates a good rate capability (calculation based on anode active mass). At 0.8 A g-1, the battery provides an average specific capacity of 130 mA h g-1, exhibiting high Coulombic efficiency (∼96%), with 95% capacity retention of over 200 cycles across its life span, which is a new achievement in the electrochemical performance of aqueous Ca-ion batteries. Furthermore, the calcium-ion storage mechanism is investigated using high-end X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements. Thus, this significant electrochemical performance of the anode and the cathode renders the battery a promising candidate in grid-scale storage applications.

Three-Dimensionally Reinforced Freestanding Cathode for High-Energy Room-Temperature Sodium-Sulfur Batteries.

Room-temperature sodium-sulfur (RT Na-S) battery cathodes suffer from poor conductivity, rapid dissolution of intermediate products, and potentially destructive volume change during cycling. The optimal way to minimize these problems could be a construction of a nanocomposite cathode scaffold combining different components selected for their particular functions. Here, we have combined the excellent electronic conductivity of reduced graphene oxide, polysulfide adsorption ability of the ultrafine manganese oxide nanocrystals, rapid ion/electron dissemination efficiency of nanosized sulfur, and outstanding mechanical stiffness and good electrical conductivity of Na alginate/polyaniline hybrid binder in a single electrode heterostructure. At 0.2 A g-1, an RT Na-S battery containing the freestanding cathode delivers an initial specific cap acity of 631 mA h g-1. By delivering a nominal discharge voltage of 1.81 V, our Na-S batteries bestow a high specific energy of 737 W h kg-1 at the 2nd cycle and 660 W h kg-1 was retained after 50 cycles. The effect of the amount of electrolyte additive is also well demonstrated in this study. The electrode fabrication process provides a new approach to tailor the design and preparation of effective cathodes for the room-temperature sodium-sulfur batteries.

Efficient HF exchange evaluation through Fourier convolution in Cartesian grid for orbital-dependent density functionals.

We present a purely numerical approach in a Cartesian grid, for efficient computation of the Hartree-Fock (HF) exchange contribution in the HF and density functional theory models. This takes inspiration from a recently developed algorithm by Liu et al., in 2017, where the rate-determining step is the accurate evaluation of electrostatic potential. This introduces the Fourier convolution theorem in conjunction with a range-separated Coulomb interaction kernel. The latter is efficiently mapped into a real grid through a simple optimization procedure, giving rise to a constraint in the range-separated parameter. The overall process offers logarithmic scaling with respect to the molecular size. It is then extended toward global hybrid functionals such as B3LYP, PBE0, and BHLYP within pseudopotential Kohn-Sham theory, through an LCAO-MO ansatz in a Cartesian grid, developed earlier in our laboratory. For the sake of comparison, a parallel semi-numerical approach has also been worked out that exploits the familiar Obara-Saika recursion algorithm without any additional techniques. An excellent agreement between these two routes is demonstrated through total energy and orbital energy in a series of atoms and molecules (including 10 π-electron molecules), employing an LANL2DZ-type basis function. A critical analysis of these two algorithms reveals that the proposed numerical scheme could lead to very attractive and competitive scaling. The success of our approach also enables us for further development of optimally tuned range-separated hybrid and hyper functionals.

Insights of Diffusion Doping in Formation of Dual-Layered Material and Doped Heterostructure SnS-Sn:Sb2S3 for Sodium Ion Storage.

Insights into the formation mechanism of a dual-layered and doped heterostructure material SnIIS-SnIV:Sb2S3 are reported. In the presence of mixed alkyl thiols, first nanotubes of Sb2S3 were formed, and upon introduction of Sn(IV), SnIIS was deposited onto the surface of these tubular structures. Upon further annealing at a constant temperature, sluggish transformation resulted in a Sn(II)S-Sn(IV) doped Sb2S3 heterostructure, which finally turned to flake-like layered doped Sb2S3 nanostructures. SnS and Sb2S3, both being layered materials, were explored for the study of Na-ion storage, and these heterostructures were observed to be superior in comparison to the individual materials as well as the final doped nanostructures. The mechanism of formation of the heterostructures, the epitaxy at the junction, the diffusion doping, and the dopant-induced axial exfoliations leading to the final doped structures were studied. The electrochemical conversions in the presence of Na ions were also investigated, and insights into the mechanisms of both are reported in this Letter.

A cadaveric study of the first dorsal compartment of the wrist and its content tendons: anatomical variations in the Indian population.

de Quervain's disease is a commonly encountered problem; its management is multimodal, and often, there is recurrence which is commonly associated with anatomical variation in the first dorsal compartment of the wrist. Our purpose was to find out the anatomical variation of the first dorsal compartment of the wrist in the general population to assess the anatomical basis of de Quervain's disease and its recurrence. In this cadaveric study, 86 wrists in 46 patients were dissected to search out the first dorsal compartment of the wrist and its content tendons, presence of septa in the compartment, and insertion of the tendons. Supernumerary tendons in the first dorsal compartment were seen in 74.41 % of cases. The most commonly found tendon arrangement was two abductor pollicis longus (APL) and one extensor pollicis brevis (EPB). In all cases, there was a fixed insertion of APL to the base of the first metacarpal. Among other sites, the most common site of insertion of APL is the trapezium, which was 56.14 %. Variations of EPB with respect to number, site of insertion, thickness, and bilaterality were also found. The presence of septations was found in 37.20 % of dissected cadaveric wrists. We had found supernumerary tendons or slips in the first dorsal compartment very commonly. The presence of a septum was less frequently found. So, it may be concluded that there is immense anatomical variation present in the first dorsal compartment of the wrist, supernumerary tendons/tendon slips are commonly found, there is a variation of insertions present in the population, septum/aberrant compartment are also present, and bilateral variations are present in the population. These variations may be responsible for recurrence and unilateral affection in de Quervain's disease.

Clusters of glycolic acid with three to six water molecules.

Semiempirical, ab initio, and density functional theory calculations are used to locate many low-energy minima on the potential energy surfaces of the CH2OHCOOH-(H2O)n complexes with n = 3,4,5,6. In the clusters with three, four, and five water molecules, the lowest-energy structure consists of a (H2O)n complex, not necessarily of lowest energy, hydrogen bonded to the carboxylic group of the glycolic acid. The lowest-energy structure for n = 6 is similar except that the water hexamer is hydrogen bonded to both the carboxylic and alpha-hydroxyl groups of the acid. In all the lowest-energy clusters, the intramolecular hydrogen bond remains intact in the glycolic acid.