Energetics and electronic structure of UAl4 with point defects

Concentration of constitutional and thermal defects in UAl4

“…We use both 80 and 120 atom supercells, each containing a single point defect. Details of all density functional theory (DFT) [23,24] calculations within the Vienna Ab initio Simulation Package (VASP) [25,26] used in the present work were described in a previous paper [15]. Supercell total energies (E T ) from spin-polarized first principles calculations were used to obtain the formation energies DE f of U m Al n compounds as:…”

“…To our best knowledge neither experimental nor theoretical investigations of the point defects energies and concentrations have been performed in the UAl 4 compound. We have recently reported [15] a thorough first principles study of UAl 4 atomic, electronic and magnetic configuration, together with an analysis of U and Al vacancies and antisites stability and electronic rearrangement taking into account the three possible aluminum sites according to Imma space group. In this paper, we use those results to estimate the energy of formation of point defects in the UAl 4 compound which we afterwards insert in a statistical thermodynamics formalism within the canonical ensemble [16,17] to predict equilibrium defect concentrations as a function of the alloy composition and temperature.…”

At the Limits of Isolobal Bonding: π-Based Covalent Magnetism in Mn2Hg5

“…The placement of filled low-energy levels next to empty, higher-energy ones creates a perfect setup for a stabilizing Lewis acid–base-type interaction (though in this case for a single electron rather than an electron pair). This model has been invoked to explain the emergence of antiferromagnetism in a variety of metallic compounds. − Using the DFT-raMO approach, we can see this effect at work in Mn 2 Hg 5 at the level of individual orbital interactions, with the adoption of diradical character by the Mn–Mn isolobal π bonds (Figure ), leading to a greater separation between bonding and antibonding levels.…”

“…This DFT-raMO approach will then be illustrated on a simple model system, CrGa 4 (Figure b), whose electronic structure is easily expressed in terms of 18-electron configurations on the Cr atoms. These steps will lay the groundwork for an exploration of the bonding and magnetism in Mn 2 Hg 5 , which will emerge as a detailed example of a phenomenon known as covalent magnetism, − in which antiferromagnetic order coexists with residual covalent bonding between the magnetized atoms.…”

Atomic interaction of the MEAM type for the study of intermetallics in the Al–U alloy

“…The calculated energy differences with respect to the pure metals are shown in Fig. 5 [67] are also shown. Deficiency of Al is dominated by the U Al (2) antisite, while excess of Al by Al U antisite, in agreement with first principles results [67].…”