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Two-dimensional layered materials, in general, and transition metal dichalcogenides, in particular, are promising as future device materials. Vanadium based dichalcogenides, i.e., VX2 (X = S, Se, and Te) are special in the class for showing a wide range of intriguing properties. Depending on the structural phases, VX2 can be metallic or semiconducting. The T-phase, i.e., the metallic one, is well known to host some exotic electronic properties like the charge density wave, anomalous Hall effect, ferromagnetism, etc., having strong bearing as an electronic device material. The H-phase, on the other hand, is also predicted to show ferromagnetism. The materials show properties strongly dependent on their physical dimensionality, a clear manifestation of quantum confinement effects. Several experimental attempts successfully demonstrated chemical and bio-medical applications also of this class of materials. Moreover, the heterostructures formed by VX2 with other electronically dissimilar materials could bring more variation in their existing properties. Therefore, the study of VX2 materials provides a fertile ground to explore several fascinating physical phenomena and their possibilities in future applications. Here, in the present paper, we have tried to review the current scenario in this particular field by highlighting some recent key findings. The paper is aimed at providing some insight into the recent theoretical and experimental achievements in this direction, especially in the context of electronic and magnetic properties in their lower physical dimensionality. This could furnish a comprehensive guiding tour toward exploration in the journey through VX2 materials.

Correction for ‘A new triazine based π-conjugated mesoporous 2D covalent organic framework: its in vitro anticancer activities’ by Sabuj Kanti Das et al., Chem. Commun., 2018, 54, 11475–11478.

No abstract available.DOI: http://dx.doi.org/10.3329/bjz.v39i2.10594 Bangladesh J. Zool. 39(2): 235-244, 2011

The recently developed AFOT code is applied to investigate the two-photon-absorbing (TPA) properties of some of the bis(styryl) benzene derivatives (BSBD) demonstrated recently to possess large TPA cross sections. The results are compared both with the earlier semi-empirical as well as the more recent density functional calculations.

We present an AM1 semi-empirical study of the two-photon absorption (TPA) properties of a number of bis (styryl)benzene derivatives. In a recent report these systems were shown to be good two-photon absorbers. An analysis based on the INDO scheme was also included to calculate the TPA properties. The present study, based on configuration interaction consisting of single and double excitations, is compared with the above INDO model with respect to the prediction of energetics and TPA properties. The results indicate qualitative agreement, but serious questions regarding the applicability of both methods remain.

For long incident pulses, measurement of two-photon absorption coefficients can be complicated by excited-state absorption. We develop here a quantitative ab initio model to determine the contribution of excited-state absorption in the interpretation of the two-photon absorption data for such materials. We present representative calculations of this effect for some selected systems. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 1039–1042, 2000

We present here a systematic first-principles study of electronic structure and local magnetic properties of Ce[Fe0.75M0.25]2 compounds, where M is a 3d, 4d or 5d transition or post-transition element, using the generalized gradient approximation of the density functional theory. The d–f band hybridizations existing in CeFe2 get modified by the impurity M in an orderly manner across a period for each impurity series: the hybridization is strongest for the Mn group impurity in the period and gets diminished on either side of it. The weakening of the d–f hybridization strength is also associated with a relative localization of the Ce 4f states with respect to the delocalized 4f states in CeFe2. The above effects are most prominent for 3d impurity series, while for 4d and 5d impurities, the hybridizations and relocalizations are relatively weak due primarily to the relatively extended nature of 4d and 5d wavefunctions. The Ce local moment is found to decrease from the CeFe2 value in proportion to the strength of relocalization, thus following almost the same orderly trend as obeyed by the d–f hybridization. Further, depending on the way the spin-up and spin-down densities of states of an impurity shift relative to the Fermi energy, the impurity local moments are highest for Mn or Fe group, reduce on either side, become zero for Ni to Ga, and are small but negative for V and Ti. The Ce hyperfine field is found to follow the M local moment in a linear fashion, and vice–versa.

We have investigated the possibility of long ranged ferromagnetic (FM) ordering in Co doped Cd28Se28 nanocluster using density functional approach. When two Co atoms substituted in Cd sites, the coupling between the magnetic ions is antiferromagnetic (AFM) and short ranged in nature. Coupling can turned to FM ordering by additional electron doping, however in that case interaction remains short ranged. For these system coupling mechanism has been discussed on the basis of the band coupling model.

The world wide effort for a transition to renewable and clean (i.e. carbon‐free) form of energy has resulted in an upsurge of interest in harnessing and utilizing Hydrogen. Apart from being the most abundant element in the universe, hydrogen offers many advantages over other fuels: it is non‐toxic, clean to use, and packs more energy per mass than any other fuel. Hydrogen energy production, storage and distribution constitute a multi‐disciplinary area of research. Coming to the material issues for solid state storage of hydrogen, the most desirable criteria are high storage capacity, satisfactory kinetics, and optimal thermodynamics. Complex hydrides involving light metals, such as Alanates, Imides, Borates, Amidoboranes etc. show impressive gravimetric efficiencies, although the hydrogen desorption temperatures turn out to be rather high. Apart from complex hydrides, there are other kinds of novel materials that have been investigated, e.g. carbon based materials activated with nano‐catalysts, clathrate ...

Niemann-Pick group of diseases are rare autosomal recessive disorders of lysosomal enzymes. These are divisible into six types depending on clinical and biochemical features. On the basis of sphingomyelinase assay in five cases of Niemann-Pick disease, three cases were classified as type IA, one as type IS and one as type IIS. Their clinicopathological profiles are compared with 17 cases reported previously from India.

A 7-year-old boy with 49,XXYYY karyotype is reported. Physical examination revealed facial dysmorphism, mild microcephaly, limitation of supination at the elbows, delayed bone age and moderate mental retardation.

Serum levels of cholesterol, triglyceride, free fatty acid (FFA) and high density lipoprotein (HDL) cholesterol were studied in 10 undernourished and 10 better nourished diabetic patients at different periods of insulin treatment and in non-diabetic controls. Serum concentrations of cholesterol, triglyceride and FFA were significantly higher in untreated diabetic patients than in control but the elevated lipid levels gradually shifted towards normal on insulin treatment. The HDL cholesterol, on the other hand, was significantly lower in untreated diabetic subjects than those in controls and the HDL cholesterol also gradually modified on insulin therapy. However, the improvement of all the lipid parameters on insulin treatment was somewhat delayed in undernourished compared to those of better nourished diabetics. These results, therefore, suggest that malnutrition interferes with the serum lipid improvement in diabetics on insulin treatment and may make them more prone to develop vascular complications.

For long incident pulses, one-photon absorption in the excited state formed following a two-photon absorption can play a very significant role in some organic materials. We develop here a quantitative model to determine the contribution of excited state absorption in the interpretation of the two-photon absorption data for such materials. We present representative calculations of this effect for some selected systems.

Metal-semiconductor (Schottky barrier) and semiconductor-semiconductor (heterojunction) interfaces show rectifying barrier heights and band offsets, which are two key quantities required to optimize the performance of a device. A large number of models and empirical theories have been put forward by various workers in the field during the last 50 years. But a proper understanding of the microscopic origin of these quantities is still missing. In this article, our focus is mainly to present a unified framework for first principles investigation of the electronic structure of epitaxial interfaces, in which one of the constituents is a semiconductor. LMTO method is now a well established tool for self-consistent electronic structure calculations of solids within LDA. Such calculations, when performed on supercell geometries, are quite successful in predicting a wide range of interface specific electronic properties accurately and efficiently. We describe here the basic formalism of this LMTO-supercell approach in its various levels of sophistication and apply it to investigate the electronic structure of A- and B-type NiSi2/Si(111) interface as a prototype metal-semiconductor system, and CaF2/Si(111) interface as a prototype insulator-semiconductor system. These are a few of the most ideal lattice matched epitaxial interfaces whose atomic and electronic structures have been extensively studied using a wide range of experimental probes. We give here a glimpse of these experimental results and discuss the success as well as limitations of LDA calculations to achieve accuracies useful for the device physicists.

A new formulation of ab initio theory is presented that treats a large molecule in terms of wavefunctions of its constituent molecular subunits (to be called fragments). The method aims to achieve near conventional ab initio accuracy but using a truncated set of fragment orbitals with a consequent drastic reduction of computing time and storage requirement.

Tight-binding linear muffin-tin orbital (TB-LMTO) method based on the local density functional theory is one of the most efficient state-of-art computational tools which yields the ground state properties of solids with satisfactory accuracies. We have deployed this method to study the cohesive, electronic, and magnetic properties of ordered intermetallics, and also used it in conjunction with the augmented space recursion (ASR) technique to study the local properties of the corresponding random binary alloys. This TB-LMTO-ASR approach is more versatile than the conventional single-site coherent potential approximation based methods, especially for alloys having large off-diagonal disorders. We illustrate the applicability of these electronic structure computational tools for first principles investigations of binary transition metal aluminides FeAl, CoAl and NiAl.

Homocystinuria was diagnosed in 15 (0.59%) cases on screening 2560 children for aminoacidopathies. The commonest presenting features were ectopia lentis (95%) and mental retardation (86%). Other features included, dental anomalies (40%), osteoporosis (40%), behavioral problems (33%) and arachnodactyly (13%). Diagnosis was confirmed by iodoplatinate staining of one dimensional paper chromatography of urine. All the 15 cases of homocystinuria were first treated with high dose oral pyridoxine. Only one case responded to pyridoxine therapy. All the other patients were started on a low methionine, High cysteine diet with folate supplementation. Only one patient showed a complete response to dietary therapy. Nonavailability and high cost of the commercially available methionine-free, cysteine-supplemented diet and late diagnosis were responsible for the poor response in the majority of our patients.

The efficacy of different inert materials and insecticides was tested against the potato tubermoth, Phthorimaea operculella (Zeller), in storage. The experiment consisted of 7 treatments using different inert materials such as sand, sawdust, rice husk, ash, two insecticides (deltamethrin and carbaryl dust) and an untreated control. The so-called 'indigenous' variety 'Lal Pakri' was used for the study. After 5 months storage each of the treatments was effective in reducing pestincidence, but no non-insecticide treatment was more effective thanany other. Both of the insecticide treatments kept the tuber free of the pest.

A time‐dependent analog of the Born–Oppenheimer approximation is derived. The resulting wave function furnishes an alternative route to obtain the vibronic corrections to the frequency‐dependent nonlinear optical effects.

We present here an approximateab initio formalism where a large molecule is treated in terms of its small subunits in such a way that both the integral generation and energy minimization problems are simplified. In this approach one can concentrate on one part of a molecular system and thus tailor the theoretical analysis to observations relating to this part of the system only.

The electronic structures of ${\mathrm{NiSi}}_{2}$/Si(111) A- and B-type interfaces are calculated within the local density approximation (LDA) using large supercells and the LMTO full-potential and ASA methods. The Schottky-barrier heights for the two interfaces differ by 0.14 eV, in agreement with experiment. The difference is caused by a partly filled interface band present in both structures. The LDA barrier heights ${E}_{F}$-${E}_{v}$ are both 0.4 eV too low, and insensitive to interface relaxations and to external potentials. The correct density-functional expression for the barrier height is ${E}_{F}$-${E}_{v}$+\ensuremath{\Delta}${v}_{\mathrm{xc}}$, where \ensuremath{\Delta}${v}_{\mathrm{xc}}$ is a nonlocal correction.

A new method is described in which important intra-atomic correlation terms are approximated in a multiconfiguration self-consistent-field (mcscf) framework without generating large Hamiltonian or Fock matrices. Descrition in terms of partially localized orbitals (plo) is preferred over the ordinarily delocalized molecular orbitals (mo). A new approach is also adopted for choosing the virtual excitations as well as for calculating the vectorcoupling coefficients.

The authors have delineated certain important aspects of the use of theoretical Compton profiles for estimating cohesive energy, energy of mixing, etc. Inclusion of electron-electron correlation in the calculation of Compton profiles seems to be essential in order to get the correct values of ground state energy differences. Some model calculations have also been performed for the energy change as a result of 'switching on' correlation in a homogeneous electron gas at zero temperature. Numerical estimates of this 'correlation energy' have been obtained for free-electron-like metals, viz Na and Li.

The Pattison-Williams method of using Fourier-transformed Compton profiles for obtaining Fermi momenta in simple metals, is extended to set up a scheme for inferringd orf band occupancies in transition metals, rare earths etc. CP measurements are reported for Ni,α-Mn andβ-Mn and then the new scheme is applied to obtain 3d occupancies in these systems. Some comments on the use of this method for other systems are also made.

In recent years it has been proved possible to predict the valence-band offsets of lattice-matched semiconductor heterojunctions1,2 to an accuracy of about 0.1 eV using density functional theory in the local approximation (LDA). We have investigated whether, for well-characterised metal-semiconductor interfaces, the Schottky-barrier heights can be calculated with similar accuracy. In this paper we report on our findings.

A novel method for the reconstruction of the electron momentum density (EMD) from directional Compton-profile data, based on the use of the radon transform, is presented. It supersedes all the previously suggested reconstruction techniques in simplicity and practicability. As an illustration, we reconstruct the EMD of vanadium, which is one of the most widely studied transition metals.

White Leghorn females were subjected to 18° C. constant temperature or 21–38° C. variable temperature for a period of 16 weeks. Changes in internal organs observed as a result of the elevated temperature included increased adrenal size and decreased thyroid and liver size. Focal necrosis of the cortical mass and, in some cases, slight granulation of the cortical tissue were observed in the adrenals. The epithelial lining of the thyroid follicles was lower. The pituitary gland showed slight hyperplasia and hypertrophy of the basophil cells. Hepatic changes were characterized by degeneration of parenchyma cells, fatty degeneration, congestion of hepatic vessels, nuclear degeneration of various types, leucocytic infiltration, and some focal necrosis.

This review focuses on a new type of para-catenated aromatic polymer being used in the preparation of high-performance films and fibers of exceptional strength, thermal stability, and environmental resistance, including inertness to essentially all common solvents. Polymers of this type include the cis- and trans-poly(p-phenylene benzobisoxazole) (PBO), the cis- and trans-forms of the corresponding poly(pphenylene benzobisthiazole) (PBT), and the structurally similar poly(5,5ʹ-bibenzoxazole-2.2ʹ-diyl-l,3-phenylene) (AAPBO) and poly(2,5-benzoxazole) (ABPBO) and their sulfurcontaining analogues. Because of their rigidity, these polymers become highly oriented in solution and some display liquid crystalline behavior. The purpose of this paper is to summarize the authorsʹ theoretical work on the structures, conformational energies, intermolecular interactions, electronic properties, electrical conductivity, and electrooptical properties of these chains, including, in some cases, the so-called articulated forms and the protonated forms known to exist in strong acids. The emphasis is on how such studies provide a molecular understanding of the unusual properties and processing characteristics of this new class of materials.