19991110: summary for NPT calcs

GOAL

Summarizing NPT results.

In an attempt to obtain reproducible oxygen MSD plots (from which to extract oxygen self diffusion coefficients) some of the previous unsuccessfull NVE calculations were repeated for the two systems $Ce^{4+}_{250}Ce^{3+}_{250}O_{875}(V_O^{\cdot \cdot })_{125}$ and $Zr_{100}Ce^{4+}_{200}Ce^{3+}_{200}O_{900}(V_O^{\cdot \cdot })_{100}$ in the NPT ensemble.

The two simulated systems should evidence the effect of the presence of zirconium, cerium reduction degree being the same.

The simulation temperature was $1773\;K$ and the ``ensemble npt hoover 0.5 0.1'' option was used in the CONTROL file of DL_POLY.

The following table shows the various NPT calcs with the corresponding NVE ones. ``Corresponding'' means that the pair of calculations are identical, but for the ensemble. In particular, the starting randomized configuration is identical for each corresponding pair.

$Ce^{4+}_{250}Ce^{3+}_{250}O_{875}(V_O^{\cdot \cdot })_{125}$
NVE	NPT
19990824	19991029
19990825	19991103
	19991108
$Zr_{100}Ce^{4+}_{200}Ce^{3+}_{200}O_{900}(V_O^{\cdot \cdot })_{100}$
NVE	NPT
19990831	19991020
19990902	19991028

Results

These are the results for the $Ce^{4+}_{250}Ce^{3+}_{250}O_{875}(V_O^{\cdot \cdot })_{125}$ system:

And these are the results for the $Zr_{100}Ce^{4+}_{200}Ce^{3+}_{200}O_{900}(V_O^{\cdot \cdot })_{100}$ system:

It seems that some parameter of the simulations is not properly tuned.