Gargi Dutta

Effects of O vacancies and C doping on dielectric properties of ZrO2: A first-principles study

The authors determine electronic properties, structural stability, and dielectric response of zirconia (ZrO2) with oxygen vacancies (O vacancies) and carbon doping (C doping) using first-principles density functional theory calculations based on pseudopotentials and a plane wave basis. They find significantly enhanced static dielectric response in zirconia with oxygen vacancies arising from a softened phonon mode. They also find that effects of carbon doping on the dielectric response are anisotropic.

Assembling Porphyrins into Extended Network Structures by Employing Aromatic Dicarboxylates: Synthesis, Metal Exchange, and Heterogeneous Catalytic Studies

Three new metal-organic porphyrinic framework compounds of zinc and 5,10,15,20-tetrakis(4-pyridyl)porphyrin (TPyP) have been synthesized under solvothermal conditions. The compounds [Zn5 (C40 H24 N8 )(C8 H4 O4 )2 (NO3 )6 (DMA)2 ] (DMA)3 (H2 O)8 (1; DMA=dimethylacetamide), [Zn3 (C40 H24 N8 )(C8 H4 O4 )2 (DMF)](DMF)5 (H2 O)12 (2), and [Zn3 (C40 H24 N8 )(C12 H6 O4 )2 (DMA)2 ](H2 O)7 (3) have two (1) and three dimensionally (2 and 3) extended structures. All the three structures contain porphyrinic units connected through the carboxylate linkers. The nitrates bind the metal centers and are not hydrogen bonded. The different binding modes of nitrate in the structure of 1 are observed for the first time in a porphyrin-based MOF. The openness of the structure allowed us to explore metal exchange through a room-temperature metathetic route. Compound 2 undergoes 100 % exchange with copper, whereas compound 3 exchanges 70 % with copper. The copper-exchanged compounds Cu∈2 and Cu∈3 were observed to be good heterogeneous catalysts for many important organic reactions. The chemo and regioselective enamination of β-ketoesters, preparation of propargylamine derivatives as well as regioselective cycloadditions of alkyne and azide (click reactions) have been carried out with good yields and selectivity. All the compounds have been characterized by PXRD, IR, UV/Vis, atomic absorption spectroscopy (AAS), and energy-dispersive X-ray spectroscopy (for Cu exchange).

Enhanced dielectric response of ZrO2 upon Ti doping and introduction of O vacancies

We determine the electronic properties and dielectric response of zirconia (ZrO2) with oxygen vacancies (O vacancies) and Ti doping using first-principles density functional theory calculations based on pseudopotentials and a plane wave basis. We find significantly enhanced static dielectric response in zirconia with Ti doping and introduction of oxygen vacancies. Softening of phonon modes are responsible for the enhanced dielectric response of doped samples compared to pure zirconia.

Impact of Coulomb Correlations on Magnetic Anisotropy in Mn 3 Ga Ferrimagnet

Traditional density functional theory (DFT) miserably fails to reproduce the experimental volume and magnetic anisotropy of D022 Mn3Ga, which has recently become one of the most sought-after materials in order to achieve a stable spin switching at low current density. Despite great progress over the last 10 years, this issue has hitherto remained unsolved. Here, taking into account the effects of strong electronic correlations beyond what is included in standard DFT, we show by comparison with the experiment that the DFT+U method is capable of quantitatively describing the volume and the magnetic anisotropy energy (MAE) in this alloy with physically meaningful choice of onsite Coulomb-U parameter. For the first time using a plane-wave code, we decompose MAE into spin channel-resolved components in order to determine spin-flip and spin-conserving contributions. The Mn atom at the tetrahedral site is identified as the primary source of the high perpendicular MAE with the most dominant spin-orbit coupling (SOC) occurring between its two orbital pairs: ↑↑ coupling and ↓↓ coupling between

Ti-doped ThO2 : a first-principles study of dielectric properties

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Reducibility of Ce1-xZrxO2: origin of enhanced oxygen storage capacity

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Electrical and structural properties of zirconia thin films prepared by reactive magnetron sputtering

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