Absolute Energy Scale

 

We would like to put to your attention the importance of determining a correct absolute energy scale when computing XAS spectra. This is particularly the case when generating composite spectra of similar species in different environments. Without appropriate calibrations the summed spectrum could contain spurious structures due to a floating energy scale of the spectra from the individual species if a correct absolute energy scale is not defined.

 

When only one site in one configuration is considered, a shift of the spectrum to coincide with experiment can be applied. Similar when variations around a fixed geometry are considered [Wernet et al., Science 304, 995 (2004)], but not when inequivalent centers are considered [C. Kolczewski and K. Hermann, J. Chem. Phys. 118, 7599 (2003)] or very different geometries are weighed together [Wilson et al., J. Phys. Chem. B 109, 10194 (2005); Cavalleri et al., Phys. Chem. Chem. Phys. 7, 2854 (2005); Odelius et al., Phys. Rev. B. 73, 024205 (2006); Cavalleri et al., J. Chem. Phys. 124, 194508 (2006); Leetmaa et al., J. Chem. Phys. 125, 244510 (2006)]. We have earlier published general procedures to obtain an absolute energy scale [Kolczewski et al., J. Chem. Phys. 115, 6426 (2001); Odelius et al., Phys. Rev. B. 73, 024205 (2006); Leetmaa et al., J. Chem. Phys. 125, 244510 (2006)] but some more specific detailed instructions may be in order. Thus, in a separate instruction page we summarize the procedure in detail within the StoBe context.

 

This instruction page is meant to assist all StoBe users. Please note also that when in doubt or in need of confirmation of the soundness of a computational model you are welcome to contact the StoBe {authors}. Our time is limited, but we do have an interest in correct results being generated from our method and code.

 

Lars G. M. Pettersson                                                               Klaus E. Hermann