Through the support of the German Research Foundation (DFG) in the early 60th Hartmann could expand his group of researchers. Among the  20 theoreticists  and about 100 scientists  working and teaching at Hartmann's Institute  were    H. L. Schläfer,  G. Gliemann, H. Sillescu, G.H. Kohlmeier, K. Helfrich, E. A. Reinsch, H. v. Hirschhausen, K. Jug, J. Heidberg, H. Heydmann, H. Kelm,  H. W. Spiess.
With the support of his group Hartmann focused on getting students interested in theoretical chemistry by arranging regular summer schools in theoretical chemistry held mostly at Konstanz/Bodensee.
1962 Hartmann started  Theoretica Chimica Acta a peer-reviewed scientific journal publishing original  research and review articles in theoretical chemistry.  Articles could be submitted in  English, German, French and also Latin, but only one article was ever written in Latin. 1984 shortly before his death Hartmann turned the editorship over to K. Ruedenberg, Iowa State University. After Ruedenberg's retirement 1997, the name of Theoretica Chimica Acta (TCA) was broadened to Theoretical Chemistry Accounts: Theory, Computation, and Modeling, still keeping its initials TCA, with the new editor Donald G. Truhlar, University of Minnesota.  TCA documents the growth of the field of theoretical chemistry  and contributed significantly to the progress of theoretical chemistry in Germany.
1965 Hartmann organized the first Theoretical Chemistry Symposia ( "Symposium für Theoretische Chemie"). The initial goal of the annual meetings was to provide a regular platform for theoreticians from Germany, Austria, and Switzerland to meet with experimentalist.  In the organization committee Hartmann was supported by  H. Labhart (Zürich), and 0.E. Polansky (Vienna) – to which at a later time W.A. Bingel (Göttingen), E. Ruch (Berlin), G. Wagniere (Zürich), and P. Schuster (Vienna) were added. Since 1992 the symposium organizer is selected by the Arbeitsgemeinschaft Theoretische Chemie (AGTC), founded to give this field a more official status in concert with the established professional organizations of chemistry, physical chemistry, and physics.  The symposium is since then the annual meeting for  theoretical chemists from the German speaking countries The location of these meetings varies in the series between Germany-Switzerland-Germany-Austria.
Through all the efforts initiated by H. Hartmann theoretical chemistry started to influence not only chemical research in Germany but slowly became an independent field for which new professorships were created at universities.