Bond valences site energy

Starting from this definition of the energy of a single bond, the total bond valence site energy BVSE(A) of a cation M can then be determined as the sum over bond valence terms for the interactions with each of the Nx adjacent anions Xj ... 

Keywords Battery materials Bond valence site energy model Ion migration pathways Solid electrolytes... 

Bond Valence Mismatch Pathways Versus Bond Valence Site Energy Pathways. 132... 

Procrystal electron density threshold for a migration pathway Bond valence site energy threshold for a migration pathway Absolute bond valence sum mismatch Bond valence sit energy of ion M Density functional theory... 

For screening purposes, bond valence or bond valence site energy (BVSE) pathway models derived from static structure models appear to be the most straightforward approach. In a range of earlier studies, it has been discussed how the bond valence method can be used to analyze ion transport pathways statistically, yielding predictions of ionic conductivity from crystal structure data and RMC- or MD-generated structure models [4, 8-10]. 

In order to overcome these challenges, we have more recently [9, 17] proposed to convert the bond valence mismatch first into an absolute contribution to the ion s (bond valence) site energy BVSE(M) so that the penalty functions for cation-cation repulsions, repuision> or deviations from the equal valence rule, AEbvri can be incorporated in a natural way according to... 

We have taken a planar geometry with equal bond lengths of 1.63 A between the nearest neighbor atoms P and N. We have considered only valence orbitals at each site, and electron contribution is taken in terms of site energy. Earlier studies showed that the effect of the bonding is negligible [35]. We have studied the cyclic... 

For the bond valence mismatch pathways, regions of low bond valence sum mismatch (and hence implicitly low site energy) for an ion M" are modeled as regions in the structure, where the bond valence sum F(M)... 

Fig. 1 Variation of B VSE along the transport path of a model cation conductor (equilibrium sites at X = 0.125 interstitial site at x = 0) when calculating the BVSE of the mobile ion along the path based on the softBV parameter and a cutoff radius of 8 A around the respective position of the mobile ion dark triangles) compared to the site energies that result from the formal application of the same conversion algorithm to conventional bond valence parameters with universally fixed value of the bond valence parameter b in combination with the first coordination shell cutoff criterion open squares). The different choice of the bond valence parameter b translates into a difference in the predicted activation energy. More importantly, for the latter approach, jumps in site energy (or of bond valence mismatch) occur along the path when the mobile ion crosses the boundaries between coordination shells (here at x 0.04 and x rj 0.08). Such artifacts when using standard bond valence conventions would render the approach less practicable...

Moreover, it has to be kept in mind that bond valence maps (or more precisely, bond valence sum mismatch maps) use bond valence units scale rather than an energy scale, and attempts to link energy or probability density to the bond valence mismatch were difficult to achieve in a general transferable way as the calculation of effective bond valence mismatches according to Eq. 1 requires scaling between bond valence terms and cation-cation (or anion-anion) repulsions or (for open structures) to discriminate between sites of identical bond valence sum based on the degree to which the equal valence rule is fulfilled. 

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