Ab initio study of size depending physical properties of Ptn clusters

SUSANA B. RAMOS DE DEBIAGGI; GABRIELA F. CABEZA; ABEL S. MALDONADO

Montevideo

Workshop; V Workshop on Novel Methods for Electronic Structure Calculations; 2013

ANII-PEDECIBA-CINQUIFIMA

Interest in the study of metal transition nanoparticles (NPs) properties is based on its numerous applications, many related to the heterogeneous catalysis process. NPs have unique properties in their physical and chemical behaviour that generally differ from the corresponding macroscopic material properties. In particular, with respect to thermodynamic properties, it has been found experimentally that the Debye temperature (QD) of Pt nanoparticles is greater than the corresponding metallic Pt [1]. The theoretical results obtained from the ab initio study of icosahedral (Ih) and cuboctahedral (Oh) clusters of Ptn (n = 2, 13, 55, 79 and 147) are presented. Properties such as the average bond length, cohesive energy per atom and magnetic moment were calculated using density functional methods and analysing their evolution with the cluster size. The structural properties results show good agreement with those reported in the literature [2]. Specifically, the magnetic moment decreases as the cluster size increases, correlating with growth in average bond distance.        In particular, vibrational densities of states were calculated for the dimer, bulk Pt and more stable systems, such as Pt13 and Pt55, both presenting Oh symmetry. Debye frequency calculated values (nD) ​​were greater than the one obtained for bulk Pt (4.66 THz), comparable to the experimental value of 4.99 THz [3]. Furthermore, this study was completed by obtaining specific heat (cv) for such systems.   References 1.      L. J. Giovanetti, et al. ?Anomalous Vibrational Properties Induced by Surface Effects in Capped Pt Nanoparticles? J. Phys. Chem. C. 111 (2007) 7599. 2.       L. Xiao, L. Wang. ?Structures of Platinum Clusters: Planar or Spherical?? J. Phys. Chem. A 108 (2004) 8605. 3.      Ch. Kittel, ?Introduction to Solid State Physics? Ed. John Wiley and Sons (1998)