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Recently, a semiempirical method for alloys based on equivalent crystal theory was introduced. The method successfully predicts the concentration dependence of the heat of formation and lattice parameter of binary alloys. A study of the parameters of the method is presented, along with new results for (gamma)Fe-Pd and (gamma)Fe-Ni alloys.
Pd3Fe is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Fe is bonded to twelve equivalent Pd atoms to form FePd12 cuboctahedra that share corners with twelve equivalent FePd12 cuboctahedra, edges with twenty-four equivalent PdFe4Pd8 cuboctahedra, faces with six equivalent FePd12 cuboctahedra, and faces with twelve equivalent PdFe4Pd8 cuboctahedra. All Fe–Pd bond lengths are 2.75 Å. Pd is bonded to four equivalent Fe and eight equivalent Pd atoms to form PdFe4Pd8 cuboctahedra that share corners with twelve equivalent PdFe4Pd8 cuboctahedra, edges with eight equivalent FePd12 cuboctahedra, edges with sixteen equivalent PdFe4Pd8 cuboctahedra, faces with four equivalent FePd12 cuboctahedra, and faces with fourteen equivalent PdFe4Pd8 cuboctahedra. All Pd–Pd bond lengths are 2.75 Å.
FePd is Tetraauricupride structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Fe is bonded to four equivalent Fe and eight equivalent Pd atoms to form distorted FeFe4Pd8 cuboctahedra that share corners with twelve equivalent FeFe4Pd8 cuboctahedra, edges with eight equivalent FeFe4Pd8 cuboctahedra, edges with sixteen equivalent PdFe8Pd4 cuboctahedra, faces with eight equivalent PdFe8Pd4 cuboctahedra, and faces with ten equivalent FeFe4Pd8 cuboctahedra. All Fe–Fe bond lengths are 2.72 Å. All Fe–Pd bond lengths are 2.69 Å. Pd is bonded to eight equivalent Fe and four equivalent Pd atoms to form distorted PdFe8Pd4 cuboctahedra that share corners with twelve equivalent PdFe8Pd4 cuboctahedra, edges with eight equivalent PdFe8Pd4 cuboctahedra, edges with sixteen equivalent FeFe4Pd8 cuboctahedra, faces with eight equivalent FeFe4Pd8 cuboctahedra, and faces with ten equivalent PdFe8Pd4 cuboctahedra. All Pd–Pd bond lengths are 2.72 Å.
Fe3Pd is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Fe is bonded to eight equivalent Fe and four equivalent Pd atoms to form FeFe8Pd4 cuboctahedra that share corners with twelve equivalent FeFe8Pd4 cuboctahedra, edges with eight equivalent PdFe12 cuboctahedra, edges with sixteen equivalent FeFe8Pd4 cuboctahedra, faces with four equivalent PdFe12 cuboctahedra, and faces with fourteen equivalent FeFe8Pd4 cuboctahedra. All Fe–Fe bond lengths are 2.64 Å. All Fe–Pd bond lengths are 2.64 Å. Pd is bonded to twelve equivalent Fe atoms to form PdFe12 cuboctahedra that share corners with twelve equivalent PdFe12 cuboctahedra, edges with twenty-four equivalent FeFe8Pd4 cuboctahedra, faces with six equivalent PdFe12 cuboctahedra, and faces with twelve equivalent FeFe8Pd4 cuboctahedra.
FePd2 crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of one FePd2 sheet oriented in the (0, 0, 1) direction. Fe is bonded to six equivalent Pd atoms to form distorted edge-sharing FePd6 cuboctahedra. All Fe–Pd bond lengths are 2.58 Å. Pd is bonded to three equivalent Fe atoms to form a mixture of distorted edge and corner-sharing PdFe3 cuboctahedra.
Pd3Fe crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Fe is bonded to six equivalent Pd atoms to form distorted FePd6 cuboctahedra that share corners with six equivalent PdPd12 cuboctahedra, edges with six equivalent FePd6 cuboctahedra, and edges with six equivalent PdPd12 cuboctahedra. All Fe–Pd bond lengths are 2.62 Å. There are four inequivalent Pd sites. In the first Pd site, Pd is bonded to three equivalent Fe and three equivalent Pd atoms to form a mixture of distorted edge and corner-sharing PdFe3Pd3 cuboctahedra. All Pd–Pd bond lengths are 2.84 Å. In the second Pd site, Pd is bonded to twelve Pd atoms to form PdPd12 cuboctahedra that share corners with six equivalent FePd6 cuboctahedra, corners with eighteen PdFe3Pd3 cuboctahedra, edges with six equivalent FePd6 cuboctahedra, edges with eighteen PdFe3Pd3 cuboctahedra, and faces with six equivalent PdPd12 cuboctahedra. All Pd–Pd bond lengths are 2.78 Å. In the third Pd site, Pd is bonded to three equivalent Fe and three equivalent Pd atoms to form distorted PdFe3Pd3 cuboctahedra that share corners with fourteen PdFe3Pd3 cuboctahedra, edges with twenty PdFe3Pd3 cuboctahedra, and faces with two equivalent PdPd16 cuboctahedra. All Pd–Fe bond lengths are 2.62 Å. All Pd–Pd bond lengths are 2.84 Å. In the fourth Pd site, Pd is bonded to sixteen Pd atoms to form PdPd16 cuboctahedra that share corners with six equivalent FePd6 cuboctahedra, corners with twenty-two PdFe3Pd3 cuboctahedra, edges with six equivalent FePd6 cuboctahedra, edges with twenty-six PdFe3Pd3 cuboctahedra, and faces with twenty PdFe3Pd3 cuboctahedra. There are a spread of Pd–Pd bond distances ranging from 2.78–5.56 Å.
Fe3Pd crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. there are two inequivalent Fe sites. In the first Fe site, Fe is bonded in a 8-coordinate geometry to two equivalent Fe and two equivalent Pd atoms. Both Fe–Fe bond lengths are 2.46 Å. Both Fe–Pd bond lengths are 2.63 Å. In the second Fe site, Fe is bonded in a distorted body-centered cubic geometry to eight Fe atoms. All Fe–Fe bond lengths are 2.58 Å. Pd is bonded in a 8-coordinate geometry to four equivalent Fe atoms.