• HEWA Y ABDULLAH

      Articles written in Bulletin of Materials Science

    • A comparative study of potential energy curves with RKRV curves for the ground states of I2, F2 and CO molecules

      HEWA Y ABDULLAH

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      The latest molecular constant potential energy curves used for the electronic ground states of I2, F2 and CO molecules are constructed by the Rydberg–Klein–Rees–Vanderslice (RKRV) method. The Morse, Rydberg, Hulbert–Hirschfelder and extended Rydberg potential functions compare each other and have good agreement with RKRV curves for these molecules. The percentage deviations from RKRV curves are drawn at the same abscissa scale. These curves show that the extended Rydberg potential energy curve deviation is <0.5−2% error to dissociation limit.

    • Enhancing the absorption of 1-chloro-1,2,2,2-tetrafluoroethane on carbon nanotubes: an ab initio study

      MOHSEN DOUST MOHAMMADI HEWA Y ABDULLAH GEORGE BISKOS SOMNATH BHOWMICK

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      We have investigated the possibility of utilizing various single-walled pristine and doped carbon nanotubes as adsorbents for the 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124) gaseous molecule. Three candidates, including pristine carbon nanotube (CNT), silicon carbide nanotube (SiCNT) and germanium-doped SiCNT (SiCGeNT) are identified and evaluated theoretically. The quantum simulations have been performed at the density functional theory (DFT) level with four different functionals (i.e., M06-2X, xB97XD, CAM-B3LYP and B3LYP-D3) with a split-valence triple-zeta basis set (6-311G(d)). We found that adsorption on the SiCGeNT is most favourable, while that on the pristine CNT yields the lowest adsorption energy. Adsorption on these nanotubes is not accompanied by an active charge-transfer phenomenon; instead, it is driven by weak van der Waals forces. The HOMO–LUMO energy gaps drastically change when the dopant atom is added to the SiCNT, thereby improving their overall adsorption capability. Among all of the adsorbents investigated here, SiCGeNT shows the most favourable for designing effective HCFC-124 nanosensors.

    • Weak intermolecular interactions of cysteine on BNNT, BNAlNT and BC$_2$NNT: a DFT investigation

      MOHSEN DOUST MOHAMMADI HEWA Y ABDULLAH

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      The study of intermolecular interactions is of great importance. This study attempted to quantitatively examine the interactions between cysteine (C$_3$H$_7$NO$_2$S) amino acid molecule with pristine boron nitride, Al-doped boronnitride and carbon boron nitride nanotubes (BNNT, BNAlNT, BC$_2$NNT, respectively) in vacuum. Quantum mechanical studies of such systems are possible in the density functional theory (DFT) framework. For this purpose, various functionals, such as B3LYP-D3, ${\omega}$B97XD and M062X, have been used. One of the most suitable basis functionals for the systems studied in this research is 6-311G(d), which has been used in both optimization calculations and calculations related to wavefunction analyses. The main part of this work is the study of various analyses that reveal the nature of the intermolecular interactions between the two components introduced above. The results of conceptual DFT, natural bond orbital, non-covalent interactions and quantum theory of atoms in molecules were consistent and in favour of physical adsorption in all systems. Al-doped nanotube provides more adsorption energy than others. The highest occupied molecular orbital and lowest unoccupied molecular orbital energy gaps were as follows: BNNT: 6.545, BNAlNT: 8.127 and BC$_2$NNT: 7.027 eV at B3LYP-D3/6-311G(d) model chemistry. The sensitivity of the adsorption increased when an amino acid molecule interacted with doped BNNT, and could be used to design a nanocarrier for cysteine amino acid.

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