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Quantum Delocalization of Hydrogen in the Li2NH Crystal Changjun Zhang, Matthew Dyer, and Ali Alavi*
 

Summary: Quantum Delocalization of Hydrogen in the Li2NH Crystal
Changjun Zhang, Matthew Dyer, and Ali Alavi*
Department of Chemistry, UniVersity of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
ReceiVed: September 1, 2005; In Final Form: October 3, 2005
By mapping out potential energy surfaces from density-functional theory (DFT) and solving a protonic
Schro¨dinger equation, we find that the H atom in a unit cell of the Li2NH crystal shows remarkably strong
quantum behavior, leading to the delocalization of H over six octahedral sites around each N. This can be
rationalized in terms of rapid coherent tunneling among these equivalent octahedral sites. Structural and
dynamical consequences of our finding are discussed. Since the Li-N-H compounds are considered promising
candidates for H-storage, understanding of these fundamental properties will be useful toward improving the
performance of the material.
Owing to its light mass, hydrogen present in materials can
exhibit significant quantum effects, such as tunneling.1 There
has been increasing interest in designing high-performance
materials with hydrogen-storage capability; such effects can be
of relevance in determining the basic properties of these systems,
including, for example, the energetics and location of H
absorption and also the diffusivity and transport. To a good
approximation, it often suffices to include the minimum amount
of quantum mechanics for the H by adding in the zero-point

  

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

 

Collections: Chemistry