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Title: Experimental evidence of new tetragonal polymorphs of silicon formed through ultrafast laser-induced confined microexplosion

Ordinary materials can transform into novel phases with new crystal structures at extraordinary high pressure and temperature applied under both equilibrium and non-equilibrium conditions 1-6. The recently developed method of ultra-short laser-induced confined microexplosions 7-9 extends the range of possible new phases by initiating a highly non-equilibrium plasma state deep inside a bulk material 7-12. Ultra-high quenching rates can help to overcome kinetic barriers to the formation of new metastable phases, while the surrounding pristine crystal confines the affected material and preserves it for further study 10-12. Here we demonstrate that ultra-rapid pressure release from a completely disordered plasma state in silicon produces several new metastable end phases quenched to ambient conditions. Their structure is determined from comparison to an ab initio random structure search which revealed six new energetically competitive potential phases, four tetragonal and two monoclinic ones. We show the presence of bt8 and st12, which have been predicted theoretically previously 13-15, but have not been observed in nature or in laboratory experiments. Additionally, the presence of the as yet unidentified silicon phase, Si-VIII and two of our other predicted tetragonal phases are highly likely within laser-affected zones. These findings pave the way for new materials with novelmore » and exotic properties.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [1] ;  [4] ;  [1]
  1. Australian National Univ., Canberra, ACT (Australia). Research School of Physics and Engineering
  2. Australian National Univ., Canberra, ACT (Australia). Electronic Materials Engineering; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical and Engineering Materials Division
  3. Univ. College London (UCL), London (United Kingdom). Dept. of Physics and Astronomy
  4. Australian National Univ., Canberra, ACT (Australia). Electronic Materials Engineering
Publication Date:
OSTI Identifier:
1265388
Grant/Contract Number:
AC05-00OR22725; DP120102980; FA9550-12-1-0482; EP/G007489/2
Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 6; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE