Browsing by Author "Caro, M."

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    Implications of ab initio energetics on the thermodynamics of Fe-Cr alloys
    Caro, Alfredo; Caro, M.; Lopasso, E. M.; Crowson, D. A. (AIP Publishing, 2006-09-01)
    The authors analyze the implications of the recently reported results of ab initio calculations of formation energies of the Fe-Cr alloy. The formation energies show a change in sign from negative to positive as Cr composition increases above similar to 10%. By developing a classic potential to evaluate the thermodynamic properties, they determine the location of the solubility limit and compare it with earlier results. A significant difference appears in a region of temperature and composition that is relevant for the nuclear applications of this alloy. Experimental results seem to confirm the validity of the location of the new solvus line. (c) 2006 American Institute of Physics.
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    Stopping power beyond the adiabatic approximation
    Caro, M.; Correa, A. A.; Artacho, E.; Caro, A. (Springer Nature, 2017-06-01)
    Energetic ions traveling in solids deposit energy in a variety of ways, being nuclear and electronic stopping the two avenues in which dissipation is usually treated. This separation between electrons and ions relies on the adiabatic approximation in which ions interact via forces derived from the instantaneous electronic ground state. In a more detailed view, in which non-adiabatic effects are explicitly considered, electronic excitations alter the atomic bonding, which translates into changes in the interatomic forces. In this work, we use time dependent density functional theory and forces derived from the equations of Ehrenfest dynamics that depend instantaneously on the time-dependent electronic density. With them we analyze how the inter-ionic forces are affected by electronic excitations in a model of a Ni projectile interacting with a Ni target, a metallic system with strong electronic stopping and shallow core level states. We find that the electronic excitations induce substantial modifications to the inter-ionic forces, which translate into nuclear stopping power well above the adiabatic prediction. In particular, we observe that most of the alteration of the adiabatic potential in early times comes from the ionization of the core levels of the target ions, not readily screened by the valence electrons.