title: Growth and dislocation studies of β-HMX.
abstract: BACKGROUND
  The defect structure of organic materials is important as it plays a major role in their crystal growth properties. It also can play a subcritical role in "hot-spot" detonation processes of energetics and one such energetic is cyclotetramethylene-tetranitramine, in the commonly used beta form (β-HMX).
  
  
  RESULTS
  The as-grown crystals grown by evaporation from acetone show prismatic, tabular and columnar habits, all with {011}, {110}, (010) and (101) faces. Etching on (010) surfaces revealed three different types of etch pits, two of which could be identified with either pure screw or pure edge dislocations, the third is shown to be an artifact of the twinning process that this material undergoes. Examination of the {011} and {110} surfaces show only one type of etch pit on each surface; however their natural asymmetry precludes the easy identification of their Burgers vector or dislocation type. Etching of cleaved {011} surfaces demonstrates that the etch pits can be associated with line dislocations. All dislocations appear randomly on the crystal surfaces and do not form alignments characteristic of mechanical deformation by dislocation slip.
  
  
  CONCLUSIONS
  Crystals of β-HMX grown from acetone show good morphological agreement with that predicted by modelling, with three distinct crystal habits observed depending upon the supersaturation of the growth solution. Prismatic habit was favoured at low supersaturation, while tabular and columnar crystals were predominant at higher super saturations. The twin plane in β-HMX was identified as a (101) reflection plane. The low plasticity of β-HMX is shown by the lack of etch pit alignments corresponding to mechanically induced dislocation arrays. On untwinned {010} faces, two types of dislocations exist, pure edge dislocations with b = [010] and pure screw dislocations with b = [010]. On twinned (010) faces, a third dislocation type exists and it is proposed that these pits are associated with pure screw dislocations with b = [010]. Graphical abstractEtch pits on the twinned (010) face of β-HMX.
authors: WESTCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Thomas Graham Building, 295 Cathedral Street, Glasgow, G1 1XL UK.
authors: Hugh G
authors: HG
authors: Gallagher
authors: WESTCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Thomas Graham Building, 295 Cathedral Street, Glasgow, G1 1XL UK.
authors: John N
authors: JN
authors: Sherwood
authors: WESTCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Thomas Graham Building, 295 Cathedral Street, Glasgow, G1 1XL UK ; Current address: Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton, Highfield Campus, Southampton, SO17 1BJ UK.
authors: Ranko M
authors: RM
authors: Vrcelj
keywords: Crystal growth; Dislocations; Energetics; Etching; HMX
references: Pharm Res. 2001 May;18(5):674-81
references: 11465425
references: J Am Chem Soc. 2007 Nov 14;129(45):13887-93
references: 17939660
references: Chem Cent J. 2015 Apr 18;9:22
references: 26000033
references: Phys Rev B Condens Matter. 1985 Oct 15;32(8):5335-5341
references: 9937748