Showing papers by "Rajendra R. Zope published in 2017"
TL;DR: The results support the hypothesis that a controlled introduction of small metal clusters to graphene is a feasible way to enhance its hydrogen gravimetric content, and it opens up the possibility of investigating other binary TMx-Ay clusters supported on graphene as promising candidates for hydrogen storage.
Abstract: Recent studies suggest that graphene decorated with light metal atoms is a feasible alternative for the design of the next generation of hydrogen storage systems, that is, materials which require a gravimetric content of at least 7.5 wt%, and an adsorption energy of 0.2–0.6 eV per H2. We present a first principles study of hydrogen adsorption in titanium, and bimetallic Ti5−xAlx (x = 1–3) and Ti7−xAlx (x = 1–4) clusters supported on graphene. Our results for Ti5, Ti4Al, Ti7, and Ti6Al show that doping titanium clusters with small amounts of aluminum does not influence the cluster stability on graphene, but that notably, it enhances its hydrogen gravimetric content up to 3.2–3.6 wt%. A further increment of the aluminum concentration was found to reduce the cluster stability and to favor hydrogen desorption, as shown by our calculations for supported Ti3Al2, Ti2Al3, TiAl4 and Ti5Al2. An analysis of atomic charges and density of states reveals the role of charge transfer and orbital interactions in the stability of hydride and dihydrogen complexes in the studied systems. Our results support the hypothesis that a controlled introduction of small metal clusters to graphene is a feasible way to enhance its hydrogen gravimetric content, and it opens up the possibility of investigating other binary TMx–Ay (TM = transition metal and A = main group) clusters supported on graphene as promising candidates for hydrogen storage.
14 citations
TL;DR: In this article, the performance of dyad acceptors in BHJ solar cells with poly(3-hexylthiophene) (P3HT) and a low optical gap co-polymer of thiophene and diketopyrrolopyrrole (PDPP2FT) was examined.
9 citations
TL;DR: The computed vibrational frequencies for selected cages, that is, Zn12S12,Zn16S16, ZN28S28 (O, S4, and S8 point groups), and Zn36S36 indicate that these cage structures correspond to local minima on the potential energy surface, and the infrared spectra calculated using large basis sets are also reported.
Abstract: We present a density functional study on the structural and electronic properties of ZnS bubble clusters, specifically, hollow cages whose spontaneous formation was previously observed in classical molecular dynamics simulations by Spano et al. [J. Phys. Chem. B 2003, 107, 10337]. The hollow ZnS cages in our study were modeled as ZnxSx [x = 12, 16, 24, 28, 36, 48, 108], and an onionlike structure was modeled as Zn96S96. The study of energetics and stability, performed using large polarized Gaussian basis sets, indicated all structures to be energetically stable with similar binding energy of 5.5–5.6 eV per ZnS pair. Further computation of electronic properties showed that these cages have large vertical ionization energies and relatively low electron affinities in the ranges of 6.8–8.1 and 1.7–3.0 eV, respectively. They have large highest occupied molecular orbital–lowest unoccupied molecular orbital gaps between 2.5 and 3.3 eV, and quasi-particle gaps vary from 6.2 eV for Zn12S12 to 4.19 for Zn108S108. T...
7 citations
01 Jan 2017
TL;DR: In this paper, the magnetic anisotropy energy of binary alloy clusters was studied and a density functional theory based method was proposed to compute the anisotropic energy with applications to binary metal clusters.
Abstract: The binary clusters of transition metal atoms form an interesting platform for studying the effects of shape, size, chemical compositions, and ordering on its magnetic properties. Notably, mixed clusters often show higher magnetic moments compared to pure elemental clusters. Due to the reduced dimension of the clusters, they tend to behave as single domain particles. One important parameter of their magnetic behavior is the magnetic anisotropy energy. In this chapter we review previous works on the magnetic anisotropy energy of binary alloy clusters, along with a density functional theory based method to compute the anisotropy energy with applications to binary metal clusters. The clusters of transition metal atoms often show high spin moments but generally are also reactive with the environment. Passivation of the surface atoms can lead to more stable clusters. We have explored one such avenue for passivation in this work. We consider the As@Ni12@As20 cluster which in the neutral state has a magnetic moment of 3 μB. We dope this cluster by substituting various numbers of Ni atoms by Mn atoms. The substitutional doping leads to spin moments located mostly on the Mn atoms. The doping also leads to symmetry breaking and as a consequence the number of structural isomers and spin ordered states for each isomer becomes very large. We have investigated all possible ferromagnetic isomers for a given number of dopants and subsequently all the possible anti-ferromagnetic states for the lowest energy structure were examined. The results show that the encapsulation within the As20 cage stabilizes the clusters and the atomization energy of the clusters increases as the number of dopant increases. These clusters have small energy barrier for reversal of magnetization and also have rich variation in configuration and spin states with many low-lying spin states.
3 citations
TL;DR: In this article, the effect of an entrapped single water molecule on the reactivity of free C60 and H2O@C60 has been examined, and it was shown that encapsulation of water does not have a significant effect on H 2O/C60 reactivity compared to C60.
3 citations