Contents lists available at ScienceDirect Chemical Physics journal homepage: www.elsevier.com/locate/chemphys Structural properties in single-component metallic nanoparticle: Insights from the simulation study R. Essajai a, ⁎ , A. Rachadi b , M. Qjani c , A. Mzerd a , N. Hassanain a a Group of STCE- Energy Research Center (ERC), Faculty of Science, Mohammed V University, B. P. 1014, Rabat, Morocco b LaMCScI, Faculty of Science, Mohammed V University, B. P. 1014, Rabat, Morocco c LCMP, Faculty of Sciences, ChouaïbDoukkali University, B. P. 20, El Jadida, Morocco ARTICLE INFO Keywords: Gold nanoparticles Size effect Surface lattice contraction Molecular Statics simulation ABSTRACT Structural analysis and surface lattice contraction of gold nanoparticles (AuNPs) bounded by low-index {1 0 0}, {1 1 0}and {1 1 1} facets, with sizes in the range of 43–28897 atoms (Diameters from 1 to 10 nm) were in- vestigated within the framework of Molecular Statics (MS) simulations based on the Embedded Atom Method (EAM) potential model. The present study provides insight into the size-dependent structural properties in AuNPs. All the numerical findings obtained in this Letter were compared with the available theoretical and experimental results. 1. Introduction Study of gold nanoparticles (AuNPs) has attracted enormous at- tention of researches around the world over the past years [1–4]. This interest is due to their unusual properties which enable them to be adopted in a variety of nanotechnological applications [5,6]. In particular, the AuNPs are easily hybridized with organic or inorganic compounds which qualify them to be used in various biomedical applications like biosensors [7], radiation therapy [8], photothermal therapy [9] and cancer cell imaging [10]. Additionally, Au nano- particles have many advantages, such as readily dispersed into na- nofluid [11] and bionanofluids [12]. Consequently, it is very im- portant to understand the properties of AuNP to better develop new materials based on them. In the past decades, growing attention has been paid to AuNPs in the hope of understanding their properties in terms of sizes and shapes. T. Barakat et al. [13], presented a detailed study of stability and energetic features of AuNPs within the framework of the thermodynamic model based on an empirical many-body potential energy function. They have shown that Au nanostructures in spherical shapes are more stable compared with other shapes. Furthermore, various studies are available to specify the structural characteristics and lack of crystallinity of AuNPs. On the one hand, experimental works on the Au nanoparticles with diameters of 1–2 nm has shown that their structures are amor- phous [14,15]. This last result is supported by empirical results of molecular dynamics simulations [16] and first principle calculations [17]. On the other hand, the experimental analysis on the local struc- ture and atomic arrangement of Au nanocrystals of diameters of 3–5 nm confirmed that they are composed of central parts (inner cores), and shell parts (free-surface and sub-surface) [18]. In the same context, additional simulations have been carried out in the other metallic na- noparticles, such as Pd and Si, the results indicated that they possess core-shell nanostructures [19,20] having very complex surface struc- tures, represented, in the different geometrical arrangement of their under-coordinated atoms [21]. Considerable attention has been dedicated to understanding the size dependence of the surface lattice contraction (SLC) of AuNPs. As well known, the driving force for SLC has been attributed to displacement of the free-surface atoms normal to nanoparticle surfaces during the re- laxation process. Experientially, the techniques used to study nano- particle structures are the electron microscopy and X-ray diffraction [22]. For instance, experimental X-ray diffraction data on Au decahe- dral nanoclusters showed an overall 2% contraction in the clusters [23]. A similar result has been found by an extended X-ray absorption fine structure, which measures the average bond distances in crystal na- nostructures [24–26]. Huang et al. [18] have studied the bonds con- traction on different directions normal to the Au nanocrystal surface, it emerges from their investigation that SLC’s is irregular along different directions, resulting from inhomogeneous relaxation. However, several studies gave only the mean value of SLC or consider nanoparticle sur- faces in spherical shapes are smooth, but the difference between the low-index facets has not yet been explored. https://doi.org/10.1016/j.chemphys.2019.110441 Received 22 April 2019; Received in revised form 5 July 2019; Accepted 6 July 2019 ⁎ Corresponding author. E-mail address: rida.essajai@gmail.com (R. Essajai). Chemical Physics 526 (2019) 110441 Available online 08 July 2019 0301-0104/ © 2019 Published by Elsevier B.V. T