NaGaSe2: A Water-Loving Multifunctional Non-Van Der Waals Layered Selenogallate

A Missing Member of Well-Known Ternary Chalcometallates, a Sodium Selenogallate, NaGaSe2, Has Been Synthesized by Employing a Polyselenide Flux and Stoichiometric Reaction. Crystal Structure Analysis using X-Ray Diffraction Techniques Reveals that It Contains Supertetrahedral Adamantane-Type Ga4Se10 Secondary Building Units. These Ga4Se10 Secondary Building Units Are Further Connected Via Corners to Form Two-Dimensional (2D) [GaSe2]∞- Layers Stacked Along the C-Axis of the Unit Cell, and the Na Ions Reside in the Interlayer Space. the Compound Has an Unusual Ability to Absorb Water Molecules from the Atmosphere or a Nonanhydrous Solvent to Form Distinct Hydrated Phases, NaGaSe2·xH2O (Where X Can Be 1 and 2), with an Expanded Interlayer Space, as Verified by X-Ray Diffraction (XRD), Thermogravimetric-Differential Scanning Calorimetry (TG-DSC), Desorption, and Fourier Transform Infrared Spectroscopy (FT-IR) Studies. the in Situ Thermodiffractogram Indicates the Emergence of an Anhydrous Phase Before 300 °C with the Decrease of Interlayer Spacings and Reverting to the Hydrated Phase within a Minute of Re-Exposure to the Environment, Supporting the Reversibility of Such a Process. Structural Transformation Induced through Water Absorption Results in an Increase of Na Ionic Conductivity by 2 Orders of Magnitude Compared to that of the Pristine Anhydrous Phase, as Verified by Impedance Spectroscopy. Na Ions from NaGaSe2 Can Be Exchanged in the Solid-State Route with Other Alkali and Alkaline Earth Metals in a Topotactic or Nontopotactic Way, Leading to 2D Isostructural and Three-Dimensional Networks, Respectively. Optical Band Gap Measurements Show a Band Gap of ∼3 EV for the Hydrated Phase, NaGaSe2·xH2O, Which is in Good Agreement with the Calculated Band Gap using a Density Functional Theory (DFT)-Based Method. Sorption Studies Further Confirm the Selective Absorption of Water over MeOH, EtOH, and CH3CN with a Maximum Water Uptake of 6 Molecules/formula Unit at a Relative Pressure, P/P0, of 0.9

Summary of the Activities of the Working Group I on High Energy and Collider Physics

This is a summary of the projects undertaken by the Working Group I on High Energy Collider Physics at the Eighth Workshop on High Energy Physics Phenomenology (WHEPP8) held at the Indian Institute of Technology, Mumbai, January 5-16, 2004. The topics covered are (i) Higgs searches (ii) supersymmetry searches (iii) extra dimensions and (iv) linear collider.Comment: summary of Working Group I at the Eighth Workshop on High Energy Physics Phenomenology (WHEPP8), I.I.T., Mumbai, January 5-16, 200

SEASONAL INCIDENCE AND LIFE HISTORY OF TOXOPTERA AURANTII (BOY, DE FONS.) ATTACKING ORANGE, CITRUS RETICULATA BLANCO

Toxoptera aurantii (Boyer de Fonscolombe) is one of the most important aphid species infesting mandarin orange (Citrus reticulata Blanco) in Darjeeling. West Bengal. This aphid pest is widely distributed and is found on the plant throughout the year having one peak population during August and September and very low population of this pest was recorded during cooler months of the year. This pest is capable of completing about 26 generations in a year from January to December, 1994 under laboratory conditions. It passes through four nymphal instars to become adult. The various stages of the life cycle are prolonged during cooler period of the year. The nymphal duration varied from 7 to 28 days and the adult longevity of the apterous morph ranged from 8 to 34 days. The nymph laying capacity by an apterous viviparous female was found to vary from 10 to 46 days

Unusual Atmospheric Water Trapping and Water Induced Reversible Restacking of 2D Gallium Sulfide Layers in NaGaS₂ Formed by Supertetrahedral Building Unit

Two new ternary materials NaGaS2 (1) and the Fe-doped phase of NaGaS2, NaFe0.135Ga0.865S2 (2), have been synthesized by employing polysulfide flux. Single crystal XRD analyses of 1 and 2 show that the structure is built up of adamantane-like Ga4S10 super tetrahedral fundamental building units. These admantane-like units are connected through their corners to form [GaS2]∞- layers that are stacked one over the other with Na ions residing in between the layers to balance the charge. Both the materials have the remarkable ability to absorb atmospheric water molecules and moisture from undried solvents as verified by TG analysis and FT-IR and XPS studies. The process of water absorption leads to stable distinct material NaGaS2·~H2O (1·H2O) and NaFe0.135Ga0.865S2·H2O (2·H2O) with restacked layers different from original crystal structure. This structural transformation is reversible as the transformed structures 1·H2O and 2·H2O can be returned to their original structures 1 and 2, respectively, upon heating. DFT calculation study reveals that a spontaneous exergonic hydration reaction takes place as outlined in NaGaS2 + H2O → NaGaS2H2O with the energy release, ΔE of -73.9 kJ mol-1. DFT calculation predicts an increase in the unit cell parameters of b and c directions and shrinkage along the a direction of hydrated phase 1·H2O with an overall volume increase of 36.6%. Structural transformation affects their physical properties as the pristine compound 1 possess Na+ ion conductivity of 2.88 x 10-7 S cm-1 at 22 ⁰C, whereas the hydrated compound 1·H2O displays ~40 times increased ion conductivity of 1.25 × 10-5 S cm-1 at the same temperature. DRS studies show very similar optical band gaps of ~4 eV for compounds 1 and 1·H2O, respectively, in reasonable agreement with the DFT(HSE) band gap estimation but more than 1 eV above the DFT(PBE)-predicted band gaps of ~2.4 eV. A sorption study indicates selective adsorption of water over MeOH, EtOH, and CH3CN with a maximum water uptake of 2.6 H2O per formula unit at P/Po= 0.9. A Karl Fischer titration study shows that NaGaS2 (1) is certainly capable of adsorbing water from wet methanol and can be useful as a fast desiccating agent

Working group report: High energy and collider physics

This is a summary of the projects undertaken by the working group I on high energy and collider physic