Evolving Structural Diversity and Metallicity in Compressed Lithium Azide
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AbstractIn pursuit of new stable nitrogen-rich phases and of a possible insulator-metal transition, the ground-state electronic structure of lithium azide, LiN3, is investigated from 1 atm to 300 GPa (∼2-fold compression) using evolutionary crystal structure exploration methods coupled with density functional theoretical calculations. Two new LiN3 phases, containing slightly reduced and well-separated N2 units, are found to be enthalpically competitive with the known lithium azide crystal structure at 1 atm. At pressures above 36 GPa nitrogen-rich assemblies begin to evolve. These incorporate NN bond formation beyond that in N2 or N3 -. N6 rings and infinite one-dimensional linear nitrogen chains (structural analogues to polyacetylene) appear. Above 200 GPa quasi-one- and two-dimensional extended puckered hexagonal and decagonal nitrogen layers emerge. The high-pressure phase featuring linear chains may be quenchable to P = 1 atm. With increasing pressure the progression in electrical conductivity is from insulator to metal. © 2013 American Chemical Society.
CitationPrasad DLVK, Ashcroft NW, Hoffmann R (2013) Evolving Structural Diversity and Metallicity in Compressed Lithium Azide. The Journal of Physical Chemistry C 117: 20838–20846. Available: http://dx.doi.org/10.1021/jp405905k.
SponsorsWe acknowledge support by the National Science Foundation, through Research Grants CHE-0910623 and DMR-0907425, and Efree (an Energy Frontier Research Center funded by the Department of Energy (Award No. DESC0001057 at Cornell)). Computational resources provided by Efree, the XSEDE network (provided by the National Center for Supercomputer Applications through Grant TG-DMR060055N), KAUST (King Abdullah University of Science and Technology) supercomputing laboratory, and Cornell’s NanoScale Facility (supported by the National Science Foundation through Grant ECS-0335765) are gratefully acknowledged.
PublisherAmerican Chemical Society (ACS)