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PUBLISHED ONLINE: 4 SEPTEMBER 2011 | DOI: 10.1038/NMAT3096 Large variation of vacancy formation energies in
 

Summary: ARTICLES
PUBLISHED ONLINE: 4 SEPTEMBER 2011 | DOI: 10.1038/NMAT3096
Large variation of vacancy formation energies in
the surface of crystalline ice
M. Watkins1,2,3
, D. Pan4
, E. G. Wang5
, A. Michaelides1,2,3
, J. VandeVondele6
and B. Slater1,3
*
Resolving the atomic structure of the surface of ice particles within clouds, over the temperature range encountered in the
atmosphere and relevant to understanding heterogeneous catalysis on ice, remains an experimental challenge. By using
first-principles calculations, we show that the surface of crystalline ice exhibits a remarkable variance in vacancy formation
energies, akin to an amorphous material. We find vacancy formation energies as low as 0.10.2 eV, which leads to a higher
than expected vacancy concentration. Because a vacancy's reactivity correlates with its formation energy, ice particles may be
more reactive than previously thought. We also show that vacancies significantly reduce the formation energy of neighbouring
vacancies, thus facilitating pitting and contributing to pre-melting and quasi-liquid layer formation. These surface properties
arise from proton disorder and the relaxation of geometric constraints, which suggests that other frustrated materials may
possess unusual surface characteristics.

  

Source: Alavi, Ali - Department of Chemistry, University of Cambridge

 

Collections: Chemistry