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1. S. Mehendale, M. Marathe, Y. Girard, V. Repain, C. Chacon, J. Lagoute, S. Rousset and S. Narasimhan,
Prediction of Reconstruction in Heteroepitaxial Systems Using the Frenkel-Kontorova Model,
Physical Review B,
84, 195458 (2011).
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2. Anders Odell, Anna Delin, Borje Johansson, Kanchan Ulman, Shobhana Narasimhan, Ivan Rungger and Stefano Sanvito,
Comparison between s- and d-electron mediated transport in a photoswitching dithienylethene molecule using ab initio transport methods,
Physical Review B,
84, 165402 (2011).
, Read abstract. The influence of the electrodes Fermi surface on the transport properties of a photoswitching molecule is investigated with state of the art ab initio transport methods. We report results for the conducting properties of the two forms of dithienylethene attached either to Ag or to non-magnetic Ni leads. The I-V curves of the Ag/dithienylethene/Ag device are found to be very similar to those reported previously for Au. In contrast, when Ni is used as electrode material the zero-bias transmission coefficient is profoundly different as a result of the role played by the Ni d bands in the bonding between the molecule and the electrodes. Intriguingly, despite these differences the overall conducting properties depend little on the electrode material. We thus conclude that electron transport in dithienylethene is, for the cases studied, mainly governed by the intrinsic electronic structure of the molecule.
3. A. Delga, J. Lagoute, V. Repain, C. Chacon, Y. Girard, M. Marathe, S. Narasimhan and S. Rousset,
Electronic Properties of Fe Clusters on a Au(111) Surface,
Physical Review B,
84, 035416 - 035417 (2011).
, Read abstract. The electronic states of self-organized Fe nanoislands on a Au(111) surface have been investigated
using low-temperature scanning tunneling microscopy and spectroscopy. We show that the local
density of state is dominated by Shockley surface states conned in the nanostructures. Comparing
the experimental dispersion diagram with a free-electron model we derive the eective mass
m=0.39 me and the band onset E0=420 meV of these states. Ab initio calculations show the
existence of the Shockley surface states in the Fe layer, in agreement with the experiment, and reveal
that they are fully spin polarized.
4. Mighfar Imam and Shobhana Narasimhan,
Magnetism of surface alloys of the type MxN1 À x/Rh(1 1 1),
Journal of Magnetism and Magnetic Materials,
323, 1873 - 1881 (2011).
, Read abstract. We present a density functional theory study on the magnetic properties of two-dimensional surface
alloys of the type MxN1 À x (M 1⁄4 Fe, Co and Ni; N 1⁄4 Pt, Au, Ag, Cd and Pb) on Rh(1 1 1) for x 1⁄40.0, 0.25,
0.33, 0.5, 0.67, 0.75 and 1.0, in two types of geometric arrangements—striped phases or linear-chain
type, and non-striped phases or mixed checkerboard type. Many pairs among these are bulk-immiscible
but show mixing on the surface. We find that the trend in the magnetic moment of surface alloys of N
with a given M follows the number of valence electrons in N: the higher the number of valence
electrons, the lower the magnetic moment. Overlayer atoms when put on hcp sites show higher
moment compared to fcc sites. In general, for a given composition x, linear-chain type structures show a
reduced magnetic moment compared to checkerboard type structures. We find that Pb, when alloyed
with magnetic elements (Fe, Co and Ni), has a lowering effect on their magnetic moments.
5. Nisha Mammen, Shobhana Narasimhan and Stefano de Gironcoli,
Tuning the Morphology of Gold Clusters by Substrate Doping,
JACS,
133, 2801 - 2802 (2011).
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, Read abstract. The morphology of small metal clusters can have a big impact on their electronic, magnetic, and chemical properties. This has been shown earlier, for example, for Au
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clusters on MgO(001), where planar and tetrahedral geometries are possible for the gold atoms. While the planar geometry is more desirable for catalytic applications, it is disfavored in the usual situation. While earlier suggestions that have been made for tilting this balance in favor of the planar isomer are of considerable fundamental interest, they do not easily lend themselves to practical applications. Here, we suggest a conceptually simple but practicable way of achieving the same goal: viz., by doping the MgO substrate with Al atoms. We show, by performing density functional theory calculations, that this stabilizes the planar over the tetrahedral arrangement by an energy difference that is linearly proportional to the dopant concentration and is insensitive to the position of the dopant atom. The charge transferred to the Au cluster also depends monotonically on the doping concentration. This work is of interest for possible applications in the field of gold nanocatalysis.
6. Alison Hatt, Brent Melot and Shobhana Narasimhan,
Harmonic and anharmonic properties of Fe and Ni: Thermal expansion, exchange-correlation
errors, and magnetism,
Physical Review B,
82, 134418 (2010).
, Read abstract. We have investigated the source of errors in ab initio calculations of thermal properties of the magnetic
metals Fe and Ni and their dependence on the form of the exchange and correlation functional. We used
density-functional theory and density-functional perturbation theory together with the quasiharmonic approxi-
mation to compute the coefficient of thermal expansion, bulk modulus and its pressure derivative, phonon
modes, and Grueneisen parameters of bcc Fe and fcc Ni. In nonmagnetic metals the main source of error in
calculated thermal properties can be attributed to evaluation of properties at incorrect lattice constants, which
in turn may be traced to the choice of exchange and correlation functional. However, for magnetic metals the
properties may be evaluated at both incorrect lattice constant and incorrect magnetic moment. This affects
vibrational properties so that it is no longer true that anharmonic errors are significantly less than errors at
harmonic order.
7. S. Mehendale, Y. Girard, V. Repain, C. Chacon, J. Lagoute, S. Rousset, M. Marathe and S. Narasimhan,
Ordered Surface Alloy of Bulk-Immiscible Components Stabilized by Magnetism,
Phys. Rev. Lett,
105, 056101 (2010).
, Read abstract. Using scanning tunneling microscopy and a diffraction experiment, we have discovered a new ordered
surface alloy made out of two bulk-immiscible components, Fe and Au, deposited on a Ru(0001)
substrate. In such a system, substrate-mediated strain interactions are believed to provide the main
driving force for mixing. However, spin-polarized ab initio calculations show that the most stable
structures are always the ones with the highest magnetic moment per Fe atom and not the ones minimizing
the surface stress, in remarkable agreement with the observations. This opens up novel possibilities for
creating materials with unique properties of relevance to device applications.
8. G. Prevot, Y. Girard, V. Repain, S. Rousset, A. Coati, Y. Garreau, J. Paul, N. Mammen and S. Narasimhan,
Elastic Displacements and Step Interactions on Metallic Surfaces: GIXD and ab initio study of Au(332),
Physical Review B,
81, 075415 (2010).
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9. P. Ghosh, R. Pushpa, S. de Gironcoli and S. Narasimhan,
Effective coordination number: a simple indicator of activation energies for NO dissociation on Rh(100) surfaces,
Physical Review B,
80, 233406 - 233506 (2009).
10. M. Marathe, M. Imam and S. Narasimhan,
Mixing and Magnetic Properties of Surface Alloys: The Role of the Substrate,
Applied Surface Science,
256, 449 - 454 (2009).
11. R. Pushpa, P. Ghosh, S. Narasimhan and S. de Gironcoli,
Effective Coordination as a Predictor of Adsorption Energies: a Model Study of NO on Rh(100) and Rh/MgO(100) Surfaces,
Physical Review B,
79, 165406 (2009).
12. M. Marathe, M. Imam and S. Narasimhan,
Elastic and chemical contributions to the stability of magnetic surface alloys on Ru(0001),
Physical Review B,
79, 085413 (2009).
13. M. Imam, M. Marathe and S. Narasimhan,
Nix Pt1−x /Rh(111): A Stable Surface Alloy with Enhanced Magnetic Moments,
Solid State Communications,
149, 559 - 563 (2009).
14. M. Imam, M. Marathe and S. Narasimhan,
Competition between elastic and chemical effects in the intermixing of Ag and Co on Rh(111),
J. Chem. Sci.,
120, 621 - 626 (2008).
15. P. Ghosh, R. Pushpa, S. de Gironcoli and S. Narasimhan,
Interplay between bonding and magnetism in the binding of NO to Rh clusters,
J. Chem. Phys.,
128, 194708 (2008).
16. R. P ushpa, U.V. Waghmare and S. Narasimhan,
Bond Stiffening in Small Nanoclusters and its Consequences,
Physical Review B,
77, 045427 (2008).
17. M Upadhyay Kahaly, S. Narasimhan and U.V. Waghmare,
Size dependence of structural, electronic, elastic and optical properties of selenium nanowires: A first-principles study,
J. Chem. Phys.,
128, 044718 (2008).
18. J. Paul and S. Narasimhan,
Effect of coordination on bond properties: A first principles study,
Bulletin of Materials Science,
31, 569 - 572 (2008).
19. A. Aravindh, + 66 other authors and S. Narasimhan (corresponding author),
Six C1−x O2 alloys: a possible route to stabilize carbon-based silica-like solids,
Solid State Communications,
144, 273 - 276 (2007).
20. P. Ghosh, S. Narasimhan, S. Jenkins and D.A. King,
Lifting of Ir(100) reconstruction by CO adsorption: an ab initio study,
J. Chem. Phys.,
126, 244701 (2007).
21. J. Bhattacharjee, S. Narasimhan and U.V. Waghmare,
Distiribution of Electron Charge Centres: A Picture of Bonding Based on Geometric Phases,
arXiv,
06, 12468 (2006).
22. R. Pushpa, S. Narasimhan and U.V. Waghmare,
Symmetries, vibrational instabilities and routes to stable structures of clusters of Al, Sn and As,
J. Chem. Phys.,
121, 5211 - 5220 (2004).
23. S. Narasimhan,
Ab Initio Calculations of Metal Surfaces,
Transactions of the Materials Research Society of Japan,
29, 19 - 24 (2004).
24. S. Narasimhan,
Stress, Strain and Charge Transfer in the Ag/Pt(111) System: A Test of Continuum Elasticity Theory,
Physical Review B,
69, 045425 - 045442 (2004).
25. Raghani Pushpa and Shobhana Narasimhan,
Reconstruction of Pt(111) and Domain Patterns on Close Packed Metal Surfaces,
Physical Review B,
67, 205418 (2003).
26. Raghani Pushpa and Shobhana Narasimhan,
Double Stripe Reconstruction of the Pt(111) Surface,
Bulletin of Materials Science,
26, 91 (2003).
27. Shobhana Narasimhan and Stefano de Gironcoli,
Exchange-correlation errors at harmonic and anharmonic orders: the case of bulk Cu,
Bulletin of Materials Science,
26, 75 (2003).
28. Shobhana Narasimhan and Pushpa Raghani,
Honeycombs, Triangles and Bright Stars: Pattern Formation on Metal Surfaces,
Physics at Surfaces and Interfaces, B.N. Dev (ed.), World Scientific, Singapore,
3 - 12 (2003).
29. Shobhana Narasimhan,
Ab Initio Lattice Dynamics of Ag(110),
Surface Science,
496, 331 (2002).
30. Raghani Pushpa and Shobhana Narasimhan,
Stars and Stripes: Nanoscale Misfit Dislocation Patterns on Surfaces,
Pure and Applied Chemistry,
74, 1663 (2002).
31. Shobhana Narasimhan and Stefano de Gironcoli,
Ab initio calculation of the thermal properties of Cu: Performance of the LDA and GGA,
Physical Review B,
65, 64302 (2001).
32. Shobhana Narasimhan,
Reversed Anisotropies and Thermal Contraction of FCC(110) surfaces,
Physical Review B,
64, 125409 (2001).
33. Shobhana Narasimhan,
Ab Initio Calculations on the Anomalous Thermal Behaviour of FCC(110) Surfaces,
Applied Surface Science,
182, 293 (2001).
34. Shobhana Narasimhan,
Surprises in the Physics of Metal Surfaces,
Journal of the Indian Institute of Science,
81, 15 (2001).
35. Shobhana Narasimhan,
Phonon Softening and the Anomalous Thermal Expansion of Ag(111),
Surface Science Letters,
417, (1998).
36. Shobhana Narasimhan and Matthias Scheffler,
A Model for the Thermal Expansion of Ag(111),
Zeitschrift fuer Physikalische Chemie,
202, 253 (1997).
37. Shobhana Narasimhan and J. W. Davenport,
An ab initio study of polytetrahedral packing: the Al-Mg system,
Physical Review B, Rapid Communications,
51, 659 (1995).
38. J. W. Davenport, N. Chetty, R. B. Marr, S. Narasimhan, J. E. Pasciak, R. F. Peierls and M. Weinert,
First Principles Pseudopotential Calculations on Aluminum and Aluminum Alloys,
The Minerals, Metals, and Materials Society,Warrendale,
(1994).
39. Shobhana Narasimhan and David Vanderbilt,
Elastic-Stress Domains and the Herringbone Reconstruction on Au(111),
Physical Review Letters,
69, 1564 (1992).
40. Shobhana Narasimhan and David Vanderbilt,
Anharmonic self energies of phonons in silicon,
Physical Review B, Rapid Communications,
43, 4541 (1991).
41. Shobhana Narasimhan and David Vanderbilt,
Lifetimes and frequency shifts of phonons in Si,
Phonons,
1, 89 (1990).
42. David Vanderbilt, S. H. Taole and Shobhana Narasimhan,
Anharmonic Elastic and Phonon Properties of Si,
Physical Review B,
40, 5657 (1989).
43. Srinivas Krishnagopal, Shobhana Narasimhan and S. H. Patil,
Multipolar Polarizabilities and Rydberg States,
J. Chem. Phys.,
83, 5772 (1985).
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