Density functional theory based screening of ternary alkali-transition metal borohydrides: A computational material design project

The dissociation of molecules, even the most simple hydrogen molecule, cannot be described accurately within density functional theory because none of the currently available functionals accounts for strong on-site correlation. This problem led to a discussion of properties that the local Kohn-Sham potential has to satisfy in order to correctly describe strongly correlated systems. We derive an analytic expression for the nontrivial form of the Kohn-Sham potential in between the two fragments for the dissociation of a single bond. We show that the numerical calculations for a one-dimensional two-electron model system indeed approach and reach this limit. It is shown that the functional form of the potential is universal, i.e., independent of the details of the two fragments.We acknowledge funding by the Spanish MEC (Grant No. FIS2007-65702-C02-01), “Grupos Consolidados UPV/EHU del Gobierno Vasco” (Grant No. IT-319-07), and the European Community through e-I3 ETSF project (Grant Agreement No. 211956).Peer reviewe

Packing Defects into Ordered Structures. Strands onTiO2

Bechstein R, Kristoffersen HH, Vilhelmsen LB, et al. Packing Defects into Ordered Structures. Strands onTiO2. Physical Review Letters. 2012;108(23): 236103

Ab Initio Study of the Sodium Intercalation and Intermediate Phases in Na0.44MnO2 for Sodium-Ion Battery

The Na0.44MnO2 structure is a promising cathode material for sodium ion batteries due to a high capacity (similar to 130 mAh/g) and good cycle performance. In this work, we present the results of density functional theory (DFT) calculations on the structural and electrochemical properties of Na0.44MnO2, combined with experiments. Seven intermediate phases and the two-phase reactions among them were found, where the calculated voltage profile agreed well with experiments. We found that the S-shaped tunnel is not empty in the deintercalated Na0.22MnO2 structure but has a partial occupancy of sodium ions. The new sodium sites were found in a limited sodium composition range (x = 0.44-0.55) which is attributed to the electrostatic interactions between sodium ions and manganese atoms. The asymmetric lattice evolution in Na0.44MnO2 as a function of sodium insertion/deinsertion is shown to be due to the Jahn-Teller effects. On the basis of this interpretation, we suggest that the Cr substitution will reduce the volume change significantly