19990712: summary for 19990614 19990617 19990702 19990707

NOTE

The apparent disagreement between the two ``standardized'' configurations 19990702 and 19990707 is overcome when a sufficiently long equilibration period is allowed. See 19990727 and 19990729.

GOAL

Summary for 19990614 19990617 19990702 19990707: trying to find (if anything is ever to be found) the relationship between configuration (i.e. how the ``random'' solid solution is set up) and the oxygen diffusion coefficient.

Results

The following are the different MSD plots for oxygen cores in the four experiments: 19990614 19990617 19990702 19990707. The only difference between the experiments is the randomization of the solid solution, all remaining degrees of freedom (both DL_POLY input parameters and physical system description (e.g. composition of the solid solution, lattice parameter)) being exactly the same.

These are the oxygen diffusion coefficients derived from the above MSD plots by applying the Einstein relation:

$$\begin{eqnarray*} MSD&=&6Dt+B \end{eqnarray*}$$

I tried to characterize somewhat quantitatively the different starting configurations by evaluating the Radial Distribution Function for some relevant ion pairs:

$$\begin{array}{rl} V_{O}^{\cdot\cdot}&V_{O}^{\cdot\cdot}\\ V... ...{Zr}^\times\\ V_{O}^{\cdot\cdot}&Zr_{Zr}^\times\\ \end{array}$$

Does not seem to highlight any particular relationship.

The two ``standardized'' configurations, 19990702 and 19990707, give nearly identical MSD plots when the equilibration period is sufficiently long. See 19990727 and 19990729