About the reliability of the Maximum Entropy Method in reconstructing electron density : the case of MgO
Articolo
Data di Pubblicazione:
2006
Citazione:
About the reliability of the Maximum Entropy Method in reconstructing electron density : the case of MgO / M. Merli, A. Pavese. - In: ZEITSCHRIFT FUR KRISTALLOGRAPHIE. - ISSN 0044-2968. - 221:9(2006), pp. 613-620. [10.1524/zkri.2006.221.9.613]
Abstract:
The reliability of the Maximum Entropy Method (MEM) to reconstruct finite temperature electron density (ED) is here discussed, investigating the case of periclase (MgO). A theoretical electron density has been generated by quantum mechanic calculations and folded with a function simulating atomic thermal motion, in order to produce a reference errorless ED [rho(r)(REF)]. The Fourier coefficients of p(r)(REF) have been calculated, and used as "observed" diffraction intensities to reconstruct via MEM the original ED. The electron density attained by MEM [rho(r)(MEM)] and rho(r)(REF) have been compared with each other (pixel-by-pixel and critical points) to assess the ability of MEM to retrieve EDs, on the basis of a set of observed structure factors. We have carried out our study varying the number of observed structure factors [i.e. sin (theta)/lambda cut-off], the nature of the prior-density [uniform density and procrystal-like model] and the way in which the prior-density is treated during MEM maximization [fixed or free to change]. We observe that (i) it is recommendable to use the prior-density as a start point only, and allow it to change during maximization; (ii) the closer is the prior-density to p(r)REF, the easier one attains by MEM a correct ED; (iii) if the prior-density is varied and a sufficient large number of observed structure factors used, then MEM tends to yield converging EDs, regardless of the prior-density chosen as a start point.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
Electron density; Maximum Entropy Method; MEM; MgO; Periclase
Elenco autori:
M. Merli, A. Pavese
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