This journal is © the Owner Societies 2014 Phys. Chem. Chem. Phys., 2014, 16, 1089--1094 | 1089 Cite this: Phys. Chem. Chem. Phys., 2014, 16, 1089 Prediction of dopant atom distribution on nanocrystals using thermodynamic arguments† Daniel G. Stroppa,* abc Luciano A. Montoro, a Antonio Campello, d Lourdes Gracia, ef Armando Beltra ´ n, e Juan Andre ´ s, e Edson R. Leite g and Antonio J. Ramirez ac A theoretical approach aiming at the prediction of segregation of dopant atoms on nanocrystalline systems is discussed here. It considers the free energy minimization argument in order to provide the most likely dopant distribution as a function of the total doping level. For this, it requires as input (i) a fixed polyhedral geometry with defined facets, and (ii) a set of functions that describe the surface energy as a function of dopant content for different crystallographic planes. Two Sb-doped SnO 2 nanocrystalline systems with different morphology and dopant content were selected as a case study, and the calculation of the dopant distributions expected for them is presented in detail. The obtained results were compared to previously reported characterization of this system by a combination of HRTEM and surface energy calculations, and both methods are shown to be equivalent. Considering its application pre-requisites, the present theoretical approach can provide a first estimation of doping atom distribution for a wide range of nanocrystalline systems. We expect that its use will support the reduction of experimental effort for the characterization of doped nanocrystals, and also provide a solution to the characterization of systems where even state-of-art analytical techniques are limited. Introduction The effective use of nanostructured components for novel technologies requires the ability to design and synthesize materials with highly controlled features in a reproducible way. Although a number of accomplishments have been reported in this direction, 1–5 improved methodologies for nanocrystal processing are required in order to fully exploit the unique material properties that arise at the nanoscale. 6,7 Such progress can only be achieved if the system features, such as morphology and surface energy distribution, can be reliably correlated with the environmental variables, such as the synth- esis configuration and the operational conditions of materials. A comprehensive description of a nanocrystalline system requires the combination of experimental and theoretical approaches due to the current limitations on the available characterization techniques with high spatial resolution. Even though breakthrough advances took place recently, 8–16 the quantitative analysis at the atomic scale is still severely restricted for individual nanocrystals. Among the various experimental limitations in this context, the most common are related to (i) the sample damage during experiments and to (ii) the low sampling provided by the available characterization techniques, which may lead to an inaccurate representation of the nanocrystalline systems. Although the dopant atom segregation analysis has been addressed for a few nanocrystalline materials, 17–21 a methodology that provides high resolution quantitative information for a representative number of nanocrystals is not currently available. Moreover, as the retrieval of statically representative data for the dopant segregation on individual nanocrystals by the available experimental approaches would require tremendous efforts, complementary theoretical approaches are required to assist the characterization of nanostructured systems. First principles calculations have been widely used together with experimental techniques in a synergistic manner. More specifically for the materials science scope, this combination is especially necessary to the investigation of nanostructured systems as many remarkable properties are related to extremely small size and time scales, which usually prevent the exclusive use of experimental approaches. 22,23 Therefore, theoretical modelling of materials based on first principles calculations a Brazilian Nanotechnology National Laboratory, 13083-970, Brazil b Ernst Ruska-Centre, Forschungszentrum Ju ¨lich, 52425, Germany. E-mail: d.stroppa@fz-juelich.de c Mechanical Engineering School, University of Campinas, 13083-860, Brazil d Institute of Mathematics, Statistics and Scientific Computing, University of Campinas, Brazil e Departament de Quı ´mica Fı ´sica i Analı ´tica, Universitat Jaume I, Spain f LIEC, Instituto de Quı ´mica, UNESP, 14800-900, Brazil g Department of Chemistry, Federal University of Sa ˜o Carlos, Brazil † Electronic supplementary information (ESI) available: First principles calcula- tions methodology and HRTEM morphology characterization are presented. See DOI: 10.1039/c3cp53427h Received 12th August 2013, Accepted 5th November 2013 DOI: 10.1039/c3cp53427h www.rsc.org/pccp PCCP PAPER Published on 11 November 2013. Downloaded by Universitat Jaume I on 07/01/2014 15:54:14. View Article Online View Journal | View Issue