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Psi-k Update Number 3 (February 2010)
With this update we would like to give you some information about the size and the growth of the scientific field of ab-initio electronic structure calculations.
It is rather difficult to obtain quantitative information. For years we used to say that the Psi-k Network represents about 2000 European scientists, including master and PhD students. But basically this was a rough guess only. The only hard number is the number of participants at Psi-k Workshops, Schools and Tutorials, which the years of the last ESF network, 2003-2008, amounted to about 1000 per year.
The present information is based on a literature search at the ISI Web of Science. A reasonable estimate can be obtained by using the following topic-keywords: 'ab initio' or 'first principle' or 'first principles' or 'density functional'.
The figure in the attachment gives the number of papers in the years 1991- 2009, which in the title, abstract or topic-keywords contain one of the above keywords. One sees a dramatic increase in the number of publications over these years by about a factor 6 from 1991 to 2009. The increase is more or less linear and clearly not exponential, amounting to about 16 000 publications worldwide in 2009, and to an annual increase of this number by about 800 - 1000 papers. The large size of these numbers makes it clearly impossible to study an important fraction of these publications, which is really a good argument for attending regularly workshops and schools in one's field in order to keep up to date with what is happening and what is new.
By introducing some more detailed keywords, such as 'local density approximation', 'GGA', 'GW', etc. the above are increased slightly by about 6-8 %. Moreover one should realize that there is still a number of 'dark' papers which do not include any of these keywords in title, abstract or keywords, but rather a short neutral sentence like 'We have calculated the energy ..' or similar, and the real information can only be found in the main text. (Even the Psi-k chairman has such papers.) Thus the total numbers of 'ab-initio papers' in 2009 could be around 20 000 instead of 16 000 (and if not in 2009 then in 2010).
An important question, which cannot be directly answered by the information available from the ISI Web of Science, concerns the number of scientists working in our field. Dirk Tunger, a colleague from the central library of the Research Center Jülich, has helped us to answer this question. Based on the above three keywords (ab-initio, first principle and density functional) the number of 'authors' of such papers in the year 2008 are obtained. Here the word 'author' refers to the nomenclature used in the ISI Web of Science, with full family name and first initial of the first (given) name, e.g. 'Gross E*'. Such an author is counted only once, even if he has more than one publication in 2008. However, different persons with the same ISI name (Gross E*) are counted only as one person. On the other hand experimental co-authors are also included in the number. Thus there might be a partial cancellation of the two effects. With these uncertainties the number of ab-initio scientists in our field are (for the year 2008):
European Union: 11 000, USA: 5 600, East Asia: 5 700.
Here 'East Asia' refers to China, Japan, Korea, Taiwan and Singapore.
These author numbers as well as the above publication numbers are enormously high, much higher than we had expected before this search. It clearly shows the tremendous growth in our field and the important role which it plays in natural sciences. However it also signals a great danger, i.e. that the number of persons performing DFT calculations and using user-friendly DFT codes produced by our members might have grown faster than the transfer of knowledge. Thus training of DFT skills should become more important than ever. The widely distributed codes now make an effort to be as 'fool-proof' as possible, and this is possible for relatively straight-forward simulations, but the need for training is clearly growing.
We thank Phivos Mavropoulos (Research Center Jülich) for his help with the literature search. A more detailed report on the statistical data will be published soon on the Psi-k website.
With best regards
Peter Dederichs, Psi-k Chairman
Volker Heine, Honorary Chairman
Professor P. H. Dederichs
IFF, Forschungszentrum Juelich
D-52425 Juelich, Germany
email Peter Dederichs