Staff directory

José Miguel Alonso Pruneda

CSIC Tenured Scientist
miguel.pruneda(ELIMINAR)@icn2.cat
Theory and Simulation

Publications

2017

  • Electrical and Thermal Transport in Coplanar Polycrystalline Graphene-hBN Heterostructures

    Barrios-Vargas J.E., Mortazavi B., Cummings A.W., Martinez-Gordillo R., Pruneda M., Colombo L., Rabczuk T., Roche S. Nano Letters; 17 (3): 1660 - 1664. 2017. 10.1021/acs.nanolett.6b04936. IF: 12.712

    We present a theoretical study of electronic and thermal transport in polycrystalline heterostructures combining graphene (G) and hexagonal boron nitride (hBN) grains of varying size and distribution. By increasing the hBN grain density from a few percent to 100%, the system evolves from a good conductor to an insulator, with the mobility dropping by orders of magnitude and the sheet resistance reaching the MΩ regime. The Seebeck coefficient is suppressed above 40% mixing, while the thermal conductivity of polycrystalline hBN is found to be on the order of 30-120 Wm-1 K-1. These results, agreeing with available experimental data, provide guidelines for tuning G-hBN properties in the context of two-dimensional materials engineering. In particular, while we proved that both electrical and thermal properties are largely affected by morphological features (e.g., by the grain size and composition), we find in all cases that nanometer-sized polycrystalline G-hBN heterostructures are not good thermoelectric materials. © 2017 American Chemical Society.


  • Electrochemical behavior of nanostructured La0.8Sr0.2MnO3 as cathodes for solid oxide fuel cells

    Sacanell J., Sánchez J.H., Rubio Lopez A.E., Martinelli H., Siepe J., Leyva A.G., Ferrari V.P., Pruneda M., Juan D., Lamas D.G. ECS Transactions; 78 (1): 667 - 675. 2017. 10.1149/07801.0667ecst. IF: 0.000

    La0.8Sr0.2MnO3 (LSM) is one of the most commonly used cathodes in Solid Oxide Fuel Cells (SOFC). In spite of the fact that nanostructured cathodes are expected to display improved performance, the high operating temperature (∼ 1000°C) of LSM-based SOFCs hinders their stability. In the present work, we have developed nanostructured cathodes prepared from LSM nanotubes of enhanced performance, allowing its use at lower temperatures (∼ 800°C). We observed that our cathodes have qualitative improvements compared with microstructured materials: firstly, the diffusion in the gas phase is optimized to a negligible level and secondly, evidence of ionic conduction is found, which is extremely rare in LSM cathodes. We propose that this important change in the electrochemical properties is due to the nanostructuration of the cathode and deserves further attention, including the exploration of other materials. © The Electrochemical Society.


  • Graphene-based synthetic antiferromagnets and ferrimagnets

    Gargiani P., Cuadrado R., Vasili H.B., Pruneda M., Valvidares M. Nature Communications; 8 (1, 699) 2017. 10.1038/s41467-017-00825-9. IF: 12.124

    Graphene-spaced magnetic systems with antiferromagnetic exchange-coupling offer exciting opportunities for emerging technologies. Unfortunately, the in-plane graphene-mediated exchange-coupling found so far is not appropriate for realistic exploitation, due to being weak, being of complex nature, or requiring low temperatures. Here we establish that ultra-thin Fe/graphene/Co films grown on Ir(111) exhibit robust perpendicular antiferromagnetic exchange-coupling, and gather a collection of magnetic properties well-suited for applications. Remarkably, the observed exchange coupling is thermally stable above room temperature, strong but field controllable, and occurs in perpendicular orientation with opposite remanent layer magnetizations. Atomistic first-principles simulations provide further ground for the feasibility of graphene-spaced antiferromagnetic coupled structures, confirming graphene's direct role in sustaining antiferromagnetic superexchange-coupling between the magnetic films. These results provide a path for the realization of graphene-based perpendicular synthetic antiferromagnetic systems, which seem exciting for fundamental nanoscience or potential use in spintronic devices. © 2017 The Author(s).


  • Oxygen Reduction Mechanisms in Nanostructured La0.8Sr0.2MnO3 Cathodes for Solid Oxide Fuel Cells

    Sacanell J., Hernández Sánchez J., Rubio López A.E., Martinelli H., Siepe J., Leyva A.G., Ferrari V., Juan D., Pruneda M., Mejía Gómez A., Lamas D.G. Journal of Physical Chemistry C; 121 (12): 6533 - 6539. 2017. 10.1021/acs.jpcc.7b00627. IF: 4.536

    In this work we outline the mechanisms contributing to the oxygen reduction reaction in nanostructured cathodes of La0.8Sr0.2MnO3 (LSM) for Solid Oxide Fuel Cells (SOFC). These cathodes, developed from LSM nanostructured tubes, can be used at lower temperatures compared to microstructured ones, and this is a crucial fact to avoid the degradation of the fuel cell components. This reduction of the operating temperatures stems mainly from two factors: (i) the appearance of significant oxide ion diffusion through the cathode material in which the nanostructure plays a key role and (ii) an optimized gas phase diffusion of oxygen through the porous structure of the cathode, which becomes negligible. A detailed analysis of our Electrochemical Impedance Spectroscopy supported by first-principles calculations point toward an improved overall cathodic performance driven by a fast transport of oxide ions through the cathode surface. (Figure Presented). © 2017 American Chemical Society.


2016

  • Noncontact atomic force microscopy and density functional theory studies of the (2×2) reconstructions of the polar AlN(0001) surface

    Chaumeton F., Robles R., Pruneda M., Lorente N., Eydoux B., Bouju X., Gauthier S., Martrou D. Physical Review B; 94 (16, 165305) 2016. 10.1103/PhysRevB.94.165305.

    Combined experimental and theoretical studies permit us to determine new protocols for growing by molecular beam epitaxy the technologically interesting N-rich aluminum nitride (AlN) surfaces. This is achieved by dosing the precursor gases at unusually low rates. With the help of calculated structures by using density functional theory and Boltzmann distribution of the reconstructed cells, we proposed to assign the measured surface obtained with a growth rate of 10 nm/h to a (2×2) reconstructed surface involving one additional N atom per unit cell. These N-rich AlN surfaces could open new routes to dope AlN layers with important implications in high-power and temperature technological applications. © 2016 American Physical Society.


2015

  • Electromechanical response at polar zigzag boundaries in hybrid monolayers

    Martinez-Gordillo R., Pruneda M. Physical Review B - Condensed Matter and Materials Physics; 91 (4, 045411) 2015. 10.1103/PhysRevB.91.045411. IF: 3.736

    First-principles calculations are used to demonstrate electromechanical control of charge and spin at zigzag-edged interfaces between graphene and boron-nitride domains in hybrid monolayers. We show how, through a direct piezoelectric effect, the interfacial bound charges and associated electric fields can be tuned by application of an external mechanical force (stress) on the system. This results in mechanical control of the edge magnetization (piezomagnetic effect), and the possibility to transform a semiconducting heterostructure into a half-metal. The inverse effect (application of an external electric field to induce a mechanical deformation) goes together with a magnetoelectric response, which under ideal conditions we estimate to be comparable to that of prototypical Cr2O3. These effects originate from the magnetic properties of graphene's zigzag edges and the dielectric properties of the boron-nitride domain, and can also be expected in any other coplanar heterostructures with polar discontinuities. © 2015 American Physical Society.


  • Polar discontinuities and 1D interfaces in monolayered materials

    Martinez-Gordillo R., Pruneda M. Progress in Surface Science; 90 (4): 444 - 463. 2015. 10.1016/j.progsurf.2015.08.001. IF: 5.696

    Interfaces are the birthplace of a multitude of fascinating discoveries in fundamental science, and have enabled modern electronic devices, from transistors, to lasers, capacitors or solar cells. These interfaces between bulk materials are always bi-dimensional (2D) 'surfaces'. However the advent of graphene and other 2D crystals opened up a world of possibilities, as in this case the interfaces become one-dimensional (1D) lines. Although the properties of 1D nanoribbons have been extensively discussed in the last few years, 1D interfaces within infinite 2D systems had remained mostly unexplored until very recently. These include grain boundaries in polycrystalline samples, or interfaces in hybrid 2D sheets composed by segregated domains of different materials (as for example graphene/BN hybrids, or chemically different transition metal dichalcogenides). As for their 2D counterparts, some of these 1D interfaces exhibit polar characteristics, and can give rise to fascinating new physical properties. Here, recent experimental discoveries and theoretical predictions on the polar discontinuities that arise at these 1D interfaces will be reviewed, and the perspectives of this new research topic, discussed. © 2015 Elsevier Ltd. All rights reserved.


2014

  • Piezoelectric monolayers as nonlinear energy harvesters

    López-Suárez, M.; Pruneda, M.; Abadal, G.; Rurali, R. Nanotechnology; 2014. 10.1088/0957-4484/25/17/175401. IF: 3.672


  • Theoretical study on the influence of the Mg2+ and Al3+ octahedral cations on the vibrational spectra of the hydroxy groups of dioctahedral 2:1 phyllosilicate models

    Hernández-Haro, N.; Ortega-Castro, J.,; Pruneda, M.,; Sainz-Díaz, C.I.,; Hernández-Laguna, A. Journal of Molecular Modeling; 20 (9): 2402. 2014. 10.1007/s00894-014-2402-6. IF: 1.867


  • Transport fingerprints at graphene superlattice Dirac points induced by a boron nitride substrate

    Martinez-Gordillo, R.; Roche, S.; Ortmann, F.; Pruneda, M. Physical Review B - Condensed Matter and Materials Physics; 2014. 10.1103/PhysRevB.89.161401. IF: 3.664


2012

  • Electrochemical ferroelectric switching: Origin of polarization reversal in ultrathin films

    Bristowe, N.C.; Stengel, M.; Littlewood, P.B.; Pruneda, J.M.; Artacho, E. Physical Review B - Condensed Matter and Materials Physics; 85 2012. 10.1103/PhysRevB.85.024106.


  • Native defects in hybrid C/BN nanostructures by density functional theory calculations

    Pruneda, J.M. Physical Review B - Condensed Matter and Materials Physics; 85 2012. 10.1103/PhysRevB.85.045422.


2010

  • Band selection and disentanglement using maximally localized Wannier functions: The cases of Co impurities in bulk copper and the Cu(111) surface

    Korytár R., Pruneda M., Junquera J., Ordejón P., Lorente N. Journal of Physics Condensed Matter; 22 (38, 385601) 2010. 10.1088/0953-8984/22/38/385601.

    We have adapted the maximally localized Wannier function approach of Souza et al (2002 Phys. Rev. B 65 035109) to the density functional theory based Siesta code (Soler et al 2002 J. Phys.: Condens. Mater. 14 2745) and applied it to the study of Co substitutional impurities in bulk copper as well as to the Cu(111) surface. In the Co impurity case, we have reduced the problem to the Co d-electrons and the Cu sp-band, permitting us to obtain an Anderson-like Hamiltonian from well defined density functional parameters in a fully orthonormal basis set. In order to test the quality of the Wannier approach to surfaces, we have studied the electronic structure of the Cu(111) surface by again transforming the density functional problem into the Wannier representation. An excellent description of the Shockley surface state is attained, permitting us to be confident in the application of this method to future studies of magnetic adsorbates in the presence of an extended surface state. © 2010 IOP Publishing Ltd.


  • Origin of half-semimetallicity induced at interfaces of C-BN heterostructures

    Pruneda, J.M. Physical Review B - Condensed Matter and Materials Physics; 81 2010. 10.1103/PhysRevB.81.161409.


  • Real-time TD-DFT simulations in dye sensitized solar cells: The electronic absorption spectrum of alizarin supported on TiO2 nanoclusters

    Sánchez-De-Armas R., Oviedo López J., San-Miguel M.A., Sanz J.F., Ordejón P., Pruneda M. Journal of Chemical Theory and Computation; 6 (9): 2856 - 2865. 2010. 10.1021/ct100289t.

    The structural and electronic properties of the alizarin dye supported on TiO2 nanoclusters have been examined by means of time-dependent density-functional (TD-DFT) calculations performed in the time-domain framework. The calculated electronic absorption spectrum of free alizarin shows a first band centered at 2.67 eV that upon adsorption features a red shift by 0.31 eV, in agreement with both experimental and previous theoretical work. This red shift arises from a relative stabilization of the dye LUMO when adsorbed. To analyze the dependence of the electronic properties of the dye-support couple on the size of metal-oxide nanoparticles, different models of (TiO 2)n nanoclusters have been used (with n = 1, 2, 3, 6, 9, 15, and 38). As a conclusion, the minimal model is good enough to theoretically reproduce the main feature in the spectrum (i.e., the energy shift of the main band upon binding to TiO2). However, it fails in creating intermediate states which could play a significant role under real experimental conditions (dynamics of the electronic transfer). Indeed, as the size of the nanocluster grows, the dye LUMO moves from the edge to well inside the conduction band (Ti 3d band). On the other hand, to assess the consistency of the time-domain approach in the case of such systems, conventional (frequency-domain) TD-DFT calculations have been carried out. It is found that, as far as the functional and basis set are equivalent, both approaches lead to similar results. While for small systems the standard TD-DFT is better suited, for medium to large sized systems, the real-time TD-DFT becomes competitive and more efficient. © 2010 American Chemical Society.


2009

  • He-LiF surface interaction potential from fast atom diffraction

    Schüller, A.; Winter, H.; Gravielle, M.S.; Pruneda, J.M.; Miraglia, J.E. PHYSICAL REVIEW A; 80 2009. 10.1103/PhysRevA.80.062903.


  • Nonadiabatic wavepacket dynamics: K-space formulation

    Pruneda, J.M.; Souza, I. Physical Review B - Condensed Matter and Materials Physics; 79 2009. 10.1103/PhysRevB.79.045127.


2008

  • The SIESTA method; Developments and applicability

    Artacho E., Anglada E., Diéguez O., Gale J.D., García A., Junquera J., Martin R.M., Ordejón P., Pruneda J.M., Sánchez-Portal D., Soler J.M. Journal of Physics Condensed Matter; 20 (6, 064208) 2008. 10.1088/0953-8984/20/6/064208.

    Recent developments in and around the SIESTA method of first-principles simulation of condensed matter are described and reviewed, with emphasis on (i) the applicability of the method for large and varied systems, (ii) efficient basis sets for the standards of accuracy of density-functional methods, (iii) new implementations, and (iv) extensions beyond ground-state calculations. © 2008 IOP Publishing Ltd.


2005

  • First-principles study of structural, elastic, and bonding properties of pyrochlores

    J.M. Pruneda; Emilio Artacho Physical Review B - Condensed Matter and Materials Physics; 2005. .


2004

  • Intrinsic point defects and volume swelling in ZrSiO4 under irradiation

    J. M. Pruneda; T. D. Archer; Emilio Artacho Physical Review B - Condensed Matter and Materials Physics; 2004. .


  • Short-range repulsive interatomic interactions in energetic processes in solids

    J. M. Pruneda; Emilio Artacho Physical Review B - Condensed Matter and Materials Physics; 2004. .