Electronic, mechanical and lattice dynamical properties of YXB (X = Cr, Mn, Fe, and Co) compounds

In this study, the physical such as structural, electronic, anisotropic elastic and lattice dynamic properties of YXB (X = Cr, Mn, Fe and Co) compounds have been investigated. The electronic properties including band structure and corresponding partial density of states for YXB have been calculated. YFeB and YCoB compounds are found to have metallic behavior while YCrB and YMnB have semiconductor behavior. Also, the compounds are found to be as non-magnetic materials. The calculated elastic constants indicate that these materials are mechanically stable due to satisfying Born stability criteria. In addition, the second order elastic constants and related polycrystalline elastic moduli (e.g. shear modulus, Young's modulus, Poisson's ratio, Debye temperature, sound velocities) are determined and the results are discussed in detail. The mechanical anisotropy is discussed using several anisotropy indexes and two-dimensional and three-dimensional surface constructions are obtained. All the compounds have dominantly covalent bonding and they are brittle materials. YCrB is found to be as a super hard material. YFeB, YCoB and YMnB are found to be as hard materials. The dynamical stability of these compounds has been studied and it has been found that YCoB is dynamically unstable. In addition, the thermodynamic properties (heat capacity, free energy, etc) of these compounds have been obtained and discussed in detail.