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Articles 1 - 13 of 13
Full-Text Articles in Physics
First-Principles Study Of Interaction Of Molecular Hydrogen With Li-Doped Carbon Nanotube Peapod Structures, Li Chen, Yiming Zhang, Nikhil Koratkar, Puru Jena, Saroj K. Nayak
First-Principles Study Of Interaction Of Molecular Hydrogen With Li-Doped Carbon Nanotube Peapod Structures, Li Chen, Yiming Zhang, Nikhil Koratkar, Puru Jena, Saroj K. Nayak
Physics Publications
Using first-principles density functional theory based on gradient corrected approach, we have studied interaction of H2 molecule with Li-doped carbon nanotube and nanotube based peapod structures. We find that H2 physisorbs on pure carbon nanotube, which is in agreement with earlier studies, and this binding increases when H2 binds to Li-decorated on carbon nanotube surfaces: the binding is further enhanced with Li atoms deposited on C60 doped nanotube peapod structures. The increase in binding in the latter structures arises due to charge transfer between the nanotube and C60, which further facilitates charge transfer from Li to the nanotube. Encapsulating fullerene …
Li- And B-Decorated Cis-Polyacetylene: A Computational Study, S. Li, Puru Jena
Li- And B-Decorated Cis-Polyacetylene: A Computational Study, S. Li, Puru Jena
Physics Publications
By using density functional theory and the generalized gradient approximation, we show that Li-decorated cis-polyacetylene meets some of the requirements of an ideal hydrogen storage material. Unlike Ti-doped cis-polyacetylene, Li resists clustering and can reversibly store up to 10.8 wt %hydrogen in molecular form. However, molecular dynamics simulations show that Li can retain hydrogen only at cryogenic temperatures. On the other hand, B-doped cis-polyacetylene can store up to 7.5 wt % hydrogen, but it binds to hydrogen too strongly to be suitable for room temperature applications. The results are compared to those in Ti-doped cis-polyacetylene.
Stability And Magnetic Properties Of T2sin (T=Cr,Mn,1≤N≤8) Clusters, R. Robles, Shiv N. Khanna, A. W. Castleman Jr
Stability And Magnetic Properties Of T2sin (T=Cr,Mn,1≤N≤8) Clusters, R. Robles, Shiv N. Khanna, A. W. Castleman Jr
Physics Publications
First-principles studies on the geometry, electronic structure, and magnetic properties of neutral and anionic Cr2Sin and Mn2Sin (1≤n≤8) have been carried out within a gradient corrected density-functional framework. We find that Cr2Sin clusters containing up to five Si atoms and Mn2Sin clusters containing up to eight Si atoms are all marked by finite local spin moments at the transition-metal site that order ferromagnetically or antiferromagnetically depending on the size and the charged state. Our studies of the variation in the binding energy upon addition of successive Si atoms and the gap between the highest occupied molecular orbital and the lowest …
Anisotropy In The Electronic Structure Of V2gec Investigated By Soft X-Ray Emission Spectroscopy And First-Principles Theory, Martin Magnuson, Ola Wilhelmsson, Maurizio Mattesini, Sa Li, Rajeev Ahuja, Olle Eriksson, Hans Högberg, Lars Hultman, Ulf Jansson
Anisotropy In The Electronic Structure Of V2gec Investigated By Soft X-Ray Emission Spectroscopy And First-Principles Theory, Martin Magnuson, Ola Wilhelmsson, Maurizio Mattesini, Sa Li, Rajeev Ahuja, Olle Eriksson, Hans Högberg, Lars Hultman, Ulf Jansson
Physics Publications
The anisotropy of the electronic structure of ternary nanolaminate V2GeC is investigated by bulk-sensitive soft x-ray emission spectroscopy. The measured polarization-dependent emission spectra of V L2,3, C K, Ge M1, and Ge M2,3 in V2GeC are compared with those from monocarbide VC and pure Ge. The experimental emission spectra are interpreted with calculated spectra using ab initio density-functional theory including dipole transition matrix elements. Different types of covalent chemical bond regions are revealed: V 3d-C 2p bonding at −3.8 eV, Ge 4p-C 2p bonding at −6 eV, and Ge 4p-C 2sinteraction mediated via the V 3d orbitals at −11 eV …
Photoelectron Spectroscopic And Theoretical Studies Of Fem−(Coronene)N (M=1,2, N=1,2) Complexes, Xiang Li, Soren Eustis, Kit H. Bowen, Anil K. Kandalam, Puru Jena
Photoelectron Spectroscopic And Theoretical Studies Of Fem−(Coronene)N (M=1,2, N=1,2) Complexes, Xiang Li, Soren Eustis, Kit H. Bowen, Anil K. Kandalam, Puru Jena
Physics Publications
Fem(coronene)n (m=1,2, n=1,2) cluster anions were generated by a laser vaporization source and studied by anion photoelectron spectroscopy. Density functional theory was used to calculate the structures and the spin multiplicities of those clusters as well as the electron affinities and photodetachment transitions. The calculated magnetic moments of Fe1(coronene)1 and Fe2(coronene)1 clusters suggest that coronene could be a suitable template on which to deposit small iron clusters and that these in turn might form the basis of an iron cluster-based magnetic material. Fe1(coronene)2 and Fe2(coronene)2 cluster anions and their corresponding neutrals prefer the sandwich-type structures, and the ground state structures …
Interaction Of Gas Molecules With Ti-Benzene Complexes, G. Chen, P. Jena, Y. Kawazoe
Interaction Of Gas Molecules With Ti-Benzene Complexes, G. Chen, P. Jena, Y. Kawazoe
Physics Publications
Using first-principles calculations based on gradient corrected density functional theory, we have studied the interaction of NH3, H2, and O2 with Ti-benzene complexes [Ti(Bz)2 and Ti2(Bz)2]. The energy barriers as the gas molecules approach the Ti-benzene complexes as well as the geometries of the ground state of these interacting complexes were obtained by starting with several initial configurations. While NH3 and H2 were found to physisorb on the Ti(Bz)2 complex, the O2 reacts with it strongly leading to dissociative chemisorption of the oxygen molecule. In contrast all the gas molecules react with the Ti2(Bz)2 complex. These studies indicate that the …
Photoelectron Spectroscopy And Theoretical Studies Of [Com(Pyrene)N]− (M=1,2 And N=1,2) Complexes, Anil K. Kandalam, Puru Jena, Xiang Li, Soren N. Eustis, Kit H. Bowen
Photoelectron Spectroscopy And Theoretical Studies Of [Com(Pyrene)N]− (M=1,2 And N=1,2) Complexes, Anil K. Kandalam, Puru Jena, Xiang Li, Soren N. Eustis, Kit H. Bowen
Physics Publications
Anion photoelectron spectroscopic experiments and density functional theory based calculations have been used to investigate the structural, electronic, and magnetic properties of neutral and anionic [Com(pyrene)n] (m,n=1–2) complexes. The calculated electron affinities and vertical transition energies of Com(pyrene)n are in good agreement with the measured values. Our results provide clear evidence for dimerization of Co atoms and formation of sandwich structures in these complexes. While the calculated spin magnetic moments of neutral Co2(pyrene)n complexes suggest a preference for ferromagnetic coupling between Co atoms, the spin magnetic moment of Co atom in Co(pyrene) and Co(pyrene)2 complexes was reduced to 1μB.
Ligand Induced Ferromagnetism In Zno Nanostructures, Qian Wang, Qiang Sun, P. Jena
Ligand Induced Ferromagnetism In Zno Nanostructures, Qian Wang, Qiang Sun, P. Jena
Physics Publications
Complementary to the experimental finding that ZnO nanoparticles become ferromagnetic when coated with N and S containing ligands such as dodecylamine and dodecanethiol [Garcia et al., Nano Lett.7, 1489 (2007)], we provide the first theoretical understanding of the origin of magnetism in ligated ZnO nanoparticles as well as the structural properties of the ligated systems by using density functional theory and generalized gradient approximation for exchange and correlation, and a cluster model for the nanoparticles. We show that N or S atoms of the ligand bind to the Zn sites. The accompanying changes in the Zn–O bond length, hybridization …
Optical Properties Of Ti3sic2 And Ti4aln3, S. Li, R. Ahuja, M. W. Barsoum, Puru Jena, B. Johansson
Optical Properties Of Ti3sic2 And Ti4aln3, S. Li, R. Ahuja, M. W. Barsoum, Puru Jena, B. Johansson
Physics Publications
The dielectric functions of the MAX phases, Ti3SiC2 and Ti4AlN3, have been determined from first principles calculations. We compared the dielectric functions and the reflectivityspectra of Ti3SiC2 and Ti4AlN3 with those of TiC and TiN. The optical spectra were analyzed by means of the electronic structure, which provides theoretical understanding of the conduction mechanism of these two phases. We found that Ti4AlN3 can be used to avoid solar heating and also increase the radiative cooling due to the increased thermal emittance as compared to TiN. Ti4AlN3 can therefore be a candidate coating material for temperature control of space vehicles.
Unique Magnetic Coupling Between Mn Doped Stannaspherenes Mn @Sn12, Anil K. Kandalam, Gang Chen, Puru Jena
Unique Magnetic Coupling Between Mn Doped Stannaspherenes Mn @Sn12, Anil K. Kandalam, Gang Chen, Puru Jena
Physics Publications
We report the density functional theory based study of the interaction between two Mn doped stannaspherenes (Mn@Sn12). The calculated results show that Mn@Sn12cluster is not only highly stable and carry a high magnetic moment, but these clusters retain their structural identity and form a stable dimer cluster. Most importantly, the magnetic coupling between the Mn@Sn12clusters depends on the relative orientation of the cages. In addition, ab initiomolecular dynamics calculations show that the dimer cluster is stable at room temperature. These results are expected to trigger further investigations on highly stable bimetallic magnetic cage complexes.
Li- And B-Decorated Cis-Polyacetylene: A Computational Study, S. Li, Puru Jena
Li- And B-Decorated Cis-Polyacetylene: A Computational Study, S. Li, Puru Jena
Physics Publications
By using density functional theory and the generalized gradient approximation, we show that Li-decorated cis-polyacetylene meets some of the requirements of an ideal hydrogen storage material. Unlike Ti-doped cis-polyacetylene, Li resists clustering and can reversibly store up to 10.8 wt %hydrogen in molecular form. However, molecular dynamics simulations show that Li can retain hydrogen only at cryogenic temperatures. On the other hand, B-doped cis-polyacetylene can store up to 7.5 wt % hydrogen, but it binds to hydrogen too strongly to be suitable for room temperature applications. The results are compared to those in Ti-doped cis-polyacetylene.
Vacancy-Induced Magnetism In Zno Thin Films And Nanowires, Qian Wang, Qiang Sun, Gang Chen, Yoshiyuki Kawazoe, Puru Jena
Vacancy-Induced Magnetism In Zno Thin Films And Nanowires, Qian Wang, Qiang Sun, Gang Chen, Yoshiyuki Kawazoe, Puru Jena
Physics Publications
Extensive calculations based on density functional theory have been carried out to understand the origin of magnetism in undoped ZnO thin films as found in recent experiments. The observed magnetism is confirmed to be due to Zn, instead of O, vacancy. The main source of the magnetic moment, however, arises from the unpaired 2p electrons at O sites surrounding the Zn vacancy with each nearest-neighbor O atom carrying a magnetic moment ranging from 0.490to0.740μB. Moreover, the study of vacancy-vacancy interactions indicates that in the ground state, the magnetic moments induced by Zn vacancies prefer to ferromagnetically couple with the antiferromagnetic …
Yellow Luminescence In Zno Layers Grown On Sapphire, M. A. Reshchikov, J. Q. Xie, B. Hertog, A. Osinsky
Yellow Luminescence In Zno Layers Grown On Sapphire, M. A. Reshchikov, J. Q. Xie, B. Hertog, A. Osinsky
Physics Publications
We conducted a detailed study of the yellow luminescence (YL) band that has a maximum of 2.19eV at 10K in undoped and N-doped ZnO layers grown on sapphire substrates. Important characteristics of this band and the related defect are established. The YL band is attributed to a transition between a shallow donor and an acceptor with an energy level ∼0.4eV above the valence band. Quenching of the YL intensity with activation energies of 85meV and 0.4eV is observed at temperatures above 100 and 320K, respectively. The YL band is possibly due to a defect complex that may include a Znvacancy.