International Journal of Physics, 2022, Vol. 10, No. 1, 70-78 Available online at http://pubs.sciepub.com/ijp/10/1/6 Published by Science and Education Publishing DOI:10.12691/ijp-10-1-6 Structural, Electronic and Mechanical Properties of Re Doped FeMnP 0.67 A 0.33 (A=Ga and Ge): A DFT Study Gabriel Kipkemei Chirchir 1 , Winfred Mueni Mulwa 1,* , Bamidele Ibrahim Adetunji 2 1 Department of Physics, Egerton University, P.0. Box 536-20115 Egerton, Kenya 2 Department of Physical Sciences, Bells University of Technology, Ota, Nigeria *Corresponding author: Received December 01, 2021; Revised February 03, 2022; Accepted February 11, 2022 Abstract The structural, electronic and mechanical properties of Re doped FeMnP 0.67 A 0.33 (A= Ga and Ge) were examined by use of density functional theory (DFT) within the generalized gradient approximations as demonstrated in Quantum ESPRESSO code. The optimized structural parameters as well as derived lattice parameters are in consistent with other computational and achievable experimental results. The computed independent elastic constants confirm the mechanical stability of the investigated materials. The computed Poisson’s and Pugh’s ratios as well as Cauchy pressure, verify that FeMn 0.67 Re 0.33 P 0.67 Ga 0.33 is the most ductile among the studied compounds. The calculated values of bulk modulus, shear modulus and Young’s modulus confirm high values of bond strength, hardness and stiffness of the investigated materials respectively. Therefore, the four compounds considered may be appropriate for industrial applications. The results report that FeMn 0.67 Re 0.33 P 0.67 Ga 0.33 compound is more ductile and mechanically stable compared to other investigated compounds. This is the first qualitative computational prediction of the elastic properties of FeMnP 0.67 Ge 0.33 , FeMnP 0.67 Ga 0.33 , FeMn 0.67 Re 0.33 P 0.67 Ge 0.33 and FeMn 0.67 Re 0.33 P 0.67 Ga 0.33 compounds and this awaits experimental ratification. The calculated electronic density of states confirms that the Re_2p states are located in the conduction band (CB) in the unite cell while Re_3d dominate the CB in the supercell. Results from the doped compounds could not be compared with experimental or computational findings because to the best of our knowledge, this has not been done. Keywords: DFT, doping, ductility, electronic density of states, mechanical stability, elastic constants Cite This Article: Gabriel Kipkemei Chirchir, Winfred Mueni Mulwa, and Bamidele Ibrahim Adetunji, “Structural, Electronic and Mechanical Properties of Re Doped FeMnP 0.67 A 0.33 (A= Ga and Ge): A DFT Study.” International Journal of Physics, vol. 10, no. 1 (2022): 70-78. doi: 10.12691/ijp-10-1-6. 1. Introduction Ferromagnets with first order conversion to the ordered state are scarce. Fe 2 P-type is an eminent example with curie temperature   = 216K . Ferromagnetism in Fe 2 P-type materials fade away through first order phase transition at   = 216K . The origination of such abnormal Tc sensitivity is not clear. A distinctive property of Fe 2 P-type is an exceptionally heavy dependence of Tc on lattice parameter adjustments as a result of substitution/doping. Fe 2 P-type compounds also attract increasing attention due to their uncommon properties, that is, they exhibit a unique property of magnetocaloric effect (MCE). Fe 2 P-type compounds mimic magnetocaloric materials in that they are ductile and mechanically stable. These two properties manifest themselves in their function under repeated magnetic and thermal cycles. This unique combination of properties suits as magnetocaloric materials for near temperature refrigeration. Research efforts have been made to study the properties of Fe 2 P-type materials both computationally [1] and experimentally [2] and a few of these compounds have been exhaustively investigated. The FeMn-based magnetocaloric materials of the form FeMnP 0.67 A 0.33 (A = Ge and Ga) with hexagonal Fe 2 P-type structure are some of the compounds which have not yet been exhaustively investigated. FeMnP 0.67 A 0.33 (A= Ga and Ge) which is an example of Fe 2 P-type compound crystalizes in a hexagonal structure belonging to the space group of P-6 ̄2m. The transition metals (Fe and Mn) occupy 3f and 3g sites and the phosphorous occupy 2c and (A= Ga and Ge) occupy the 1b site. It has been observed that close to the room temperature, this group of materials, undergoes first-order magneto-elastic transition [3] which leads to changes in the ratio of the lattice parameters (c/a) without significant changes in the volume. For Fe 2 P-type materials, first order conversion is expected to rise from an interaction between magnetic, structural and electronic properties [4,5]. This study addresses the structural, electronic and mechanical properties. For the purpose of tuning the curie temperature and reducing the thermal hysteresis while enhancing the mechanical stability in Fe 2 P-type materials, a lot investigations have been carried out [6]. Balancing the Mn:Fe ratio [7] has been tried, not