Chapter 31 Structural and Mechanical Properties of NiCoMnSn Compound for Magnetic Refrigeration Close to Ambient Temperature Meriem Boudoukhani, Younes Chiba, and Malika Amari Abstract Scientific knowledge in the field of magnetic refrigeration in the vicinity of room temperature has aroused great interest in recent years because of its high energy efficiency, while having a low environmental impact, which is why much work is being done on materials to advance and control the entire chain from material to application through characterization. Quaternary Heusler alloys have received considerable attention in the development of magnetic materials to study, design and develop magnetic refrigeration systems near room temperature. The aim of this study is to optimize the thermal and structural behavior of a quaternary NiCoMnSn alloy for the concentrations x = 0, 1/4, 1/2, and 3/4; using CASTEP numerical modeling code based on quantum mechanics and density functional theory for the solution of the Schrodinger equation. The main predictors obtained allow us to state that the structure in the ferromagnetic state is more stable; and this makes this material a good candidate for different applications. Keywords Magnetic refrigeration · Heusler alloy · CASTEP 31.1 Introduction Magnetic refrigeration has aroused considerable interest mainly due to its high energy efficiency and the absence of environmentally hazardous refrigerants; that is, the heating or cooling of magnetic materials in response to the application or removal of an external magnetic field. Materials belonging to the quarter-year Heusler alloy family have received considerable attention in these studies, and are known for their semi-metallic character and which is becoming increasingly popular in future indus- tries. Quaternary Heusler alloys are intermetallic compounds with the stoichiometric composition XX ′ YZ, where X, X ′ and Y are transition metal elements and Z is an M. Boudoukhani (B ) Materials and Environmental Laboratory (LME), University of Medea, Medea, Algeria Y. Chiba · M. Amari Mechanical Engineering, Faculty of Technology, Medea University, Medea, Algeria © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 Y. Chiba et al. (eds.), Advances in Green Energies and Materials Technology, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-0378-5_31 231