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Relativistic quantum chemical calculations show that the uranium molecule U2 has a quadruple bond

Nature Chemistryvolume 11pages4044 (2019) | Download Citation


Understanding the bonding, reactivity and electronic structure of actinides is lagging behind that of the rest of the periodic table. This can be partly explained by the challenges that one faces in experimental studies of such radioactive compounds and also by the need to properly account for relativistic effects in theoretical studies. A further challenge is the very complicated electronic structures encountered in actinide chemistry, as vividly illustrated by the naked diuranium molecule U2. Here we report a computational study of this emblematic molecule using state-of-the-art relativistic quantum chemical methods. Notably, the variational inclusion of spin–orbit interactions leads not only to a different electronic ground state, but also to a lower bond multiplicity compared with those in previous studies.

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We thank the Danish Center for Scientific Computing for ample computational resources. We thank T. Helgaker and E. Uggerud (University of Oslo) for help with Gorokhov et al.34. We thank C. K. Elmar for preparing the graphical abstract. S.K. acknowledges fruitful discussions with P. Pyykkö (University of Helsinki) on numerous occasions. S.K. thanks M. Reiher (ETH Zürich) for his continuous support. We dedicate this paper to the memory of B. Roos, an outstanding quantum chemist.

Author information


  1. Laboratorium für Physikalische Chemie, ETH Zürich, Zurich, Switzerland

    • Stefan Knecht
  2. Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense, Denmark

    • Hans Jørgen Aa. Jensen
  3. Laboratoire de Chimie et Physique Quantiques, IRSAMC, Université Paul Sabatier Toulouse III, Toulouse, France

    • Trond Saue
  4. Centre for Advanced Study, Norwegian Academy of Science and Letters, Oslo, Norway

    • Trond Saue


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S.K. ran all calculations reported in this paper, whereas the interpretation of the results and the preparation of the manuscript was a joint effort by all three authors. The generalized EBO (equation (2)) was developed by S.K. and T.S.

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The Authors declare no competing interests.

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Correspondence to Stefan Knecht.

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