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Rajendra R. Zope

Bio: Rajendra R. Zope is an academic researcher from University of Texas at El Paso. The author has contributed to research in topics: Density functional theory & Dipole. The author has an hindex of 26, co-authored 120 publications receiving 2319 citations. Previous affiliations of Rajendra R. Zope include United States Naval Research Laboratory & George Washington University.


Papers
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Journal ArticleDOI
TL;DR: Semiempirical interatomic potentials have been developed for Al, T, and Ti within the embedded atom method (EAM) formalism by fitting to a large database of experimental as well as ab initio data as mentioned in this paper.
Abstract: Semiempirical interatomic potentials have been developed for Al, $\ensuremath{\alpha}\ensuremath{-}\mathrm{Ti},$ and $\ensuremath{\gamma}\ensuremath{-}\mathrm{TiAl}$ within the embedded atom method (EAM) formalism by fitting to a large database of experimental as well as ab initio data. The ab initio calculations were performed by the linearized augmented plane wave (LAPW) method within the density functional theory to obtain the equations of state for a number of crystal structures of the Ti-Al system. Some of the calculated LAPW energies were used for fitting the potentials while others for examining their quality. The potentials correctly predict the equilibrium crystal structures of the phases and accurately reproduce their basic lattice properties. The potentials are applied to calculate the energies of point defects, surfaces, and planar faults in the equilibrium structures. Unlike earlier EAM potentials for the Ti-Al system, the proposed potentials provide a reasonable description of the lattice thermal expansion, demonstrating their usefulness for molecular-dynamics and Monte Carlo simulations at high temperatures. The energy along the tetragonal deformation path (Bain transformation) in $\ensuremath{\gamma}\ensuremath{-}\mathrm{TiAl}$ calculated with the EAM potential is in fairly good agreement with LAPW calculations. Equilibrium point defect concentrations in $\ensuremath{\gamma}\ensuremath{-}\mathrm{TiAl}$ are studied using the EAM potential. It is found that antisite defects strongly dominate over vacancies at all compositions around stoichiometry, indicating that $\ensuremath{\gamma}\ensuremath{-}\mathrm{TiAl}$ is an antisite disorder compound, in agreement with experimental data.

518 citations

Journal ArticleDOI
TL;DR: In this article, the atomic structure and the energetics of H2 adsorption on Pdn (n = 1-4) clusters supported on graphene monovacancies were described.
Abstract: We give a detailed description of the atomic structure and the energetics of H2 adsorption on Pdn (n = 1–4) clusters supported on graphene monovacancies. The large binding energy of small Pdn clusters on these vacancies is a result of strong hybridization between the unsaturated carbon and the Pd atoms, and it further indicates that anchoring avoids migration of Pd clusters on the graphene surface. We found that the binding energy of a single H2 is dependent on both the Pd cluster size and the adsorption site. In general, the H2 bond cleavage is favored by Pd clusters, indicating the formation of metal hydrides. Our calculations predict that the sequential binding energy of H2 decreases from 1.2 to 0.085 eV as a function of the number of adsorbed molecules and that the graphene surface modulates the metal–hydrogen interaction. The analysis of the absorption energies and H2 average bond lengths suggest that the supported Pd4 cluster is a unique species and potential hydrogen storage candidate because it is...

74 citations

Journal ArticleDOI
TL;DR: In this paper, a new class of electronically stable boron nanostructures, viz., 60 n 2 Boron fullerene family, boroni nanotubes, and a planar B 60 BORON sheet, was proposed.

71 citations

Journal ArticleDOI
TL;DR: In this article, the existence of stable boron sheets composed of triangular and hexagonal motifs has been shown and all electron density-functional calculations on the $60{n}^{2}$ carbon icosahedral fullerene series were conducted.
Abstract: We demonstrate the existence of a family of stable boron fullerenes containing $80{n}^{2}$ atoms that is related to the family of $60{n}^{2}$ carbon icosahedral fullerene series and is compatible with the recently proposed stable boron sheets composed of triangular and hexagonal motifs. All electron density-functional calculations on the ${\text{B}}_{320}$, ${\text{B}}_{720}$, ${\text{B}}_{1280}$, and ${\text{B}}_{2000}$ confirm their stability and show that the quantum size effects open up electronic band gaps in the boron fullerenes at ${\text{B}}_{1280}$. Boron fullerenes below ${\text{B}}_{2000}$ have valence electronic structure identical to their corresponding carbon cousins from $60{n}^{2}$ family.

63 citations

Journal ArticleDOI
TL;DR: In this paper, the structural and electronic properties of titanium-and nickel-doped defective graphene nanoplatelets have been investigated for hydrogen storage, and it was shown that H2 bond cleavage is favored by defective graphene nanlatelets because of the strong interaction between the hydrogen 1s and titanium 3d levels that leads to the formation of metal hydrides.
Abstract: We report a detailed theoretical investigation of the structural and electronic properties of titanium- and nickel-doped defective graphene nanoplatelets, which are shown to be efficient materials for hydrogen storage. We found that H2 bond cleavage is favored by Ti4-doped defective graphene nanoplatelets because of the strong interaction between the hydrogen 1s and titanium 3d levels that leads to the formation of metal hydrides, while H2 adsorption on Ni4-doped defective graphene favors the formation of Kubas complexes as hydrogen 1s levels only interact with the nickel 4s levels. A comparison between adsorption energies, number of H2 adsorbed molecules, and hydrogen gravimetric content shows that Ti4-doped graphene has a better performance for hydrogen storage with a notably high hydrogen gravimetric content of 3.4 wt %; than Ni4-doped graphene with a 10-fold lower gravimetric content of only 0.30 wt %. This observation can be explained by three factors: Ti is a lighter transition metal, it absorbs a l...

59 citations


Cited by
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28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
01 Apr 1988-Nature
TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

9,929 citations

01 Feb 1995
TL;DR: In this paper, the unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio using DFT, MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set.
Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

1,652 citations

Journal ArticleDOI
TL;DR: The first comprehensive set of property-optimized augmented basis sets for elements H-Rn except lanthanides is constructed and the efficiency of the basis sets is demonstrated by computing static polarizabilities of icosahedral fullerenes up to C(720) using hybrid density functional theory.
Abstract: With recent advances in electronic structure methods, first-principles calculations of electronic response properties, such as linear and nonlinear polarizabilities, have become possible for molecules with more than 100 atoms. Basis set incompleteness is typically the main source of error in such calculations since traditional diffuse augmented basis sets are too costly to use or suffer from near linear dependence. To address this problem, we construct the first comprehensive set of property-optimized augmented basis sets for elements H–Rn except lanthanides. The new basis sets build on the Karlsruhe segmented contracted basis sets of split-valence to quadruple-zeta valence quality and add a small number of moderately diffuse basis functions. The exponents are determined variationally by maximization of atomic Hartree–Fock polarizabilities using analytical derivative methods. The performance of the resulting basis sets is assessed using a set of 313 molecular static Hartree–Fock polarizabilities. The mean...

1,277 citations