Extended Unit Cell Model Employing Two Vectors for Crystal Structure Analysis in IrPd Nanoparticles for Catalysis

Crystal structure is closely related to the function of materials, and understanding of crystal structure is essential not only in the scientific field but also in the industrial field for applications of materials. We introduce the extended unit cell (EUC) model with two vectors to effectively represent complex nanoparticle structures such as twinning and multiple twinning. This model overcomes the limitations of conventional single- and two-phase analyses in capturing such structures. Furthermore, the local atomic distribution in Ir–Pd bimetallic NPs was investigated in detail, and it was found that Ir and Pd are at sites represented by a single vector while suggesting the localized presence of Ir at sites where the vector changes. Such a detailed observation of local atomic distribution is difficult to represent by conventional two-phase analysis, highlighting the great advantage of our proposed EUC model. This study not only aims to enhance the understanding of nanoparticle structures and their properties for catalysis but also proposes a methodology that significantly reduces computational costs by simplifying the representation of complex structures. It is particularly suitable for catalytic applications requiring precise structural control.