Organic molecular crystals are often noncubic and contain significant steric hindrance within their structure to resist dislocation motion. Plastic deformation in these systems can be imparted during processing (tableting and comminution of powders), and the defect density impacts subsequent properties and performance. This paper measured the elastic and plastic properties of representative monoclinic, orthorhombic, and triclinic molecular crystalline structures using nanoindentation of as-grown sub-mm single crystals. The variation in modulus due to in-plane rotational orientation, relative to a Berkovich tip, was approximately equal to the variation of a given crystal at a fixed orientation. The onset of plasticity occurs consistently at shear stresses between 1 and 5% of the elastic modulus in all three crystal systems, and the hardness to modulus ratio suggests conventional Berkovich tips do not generate fully self-similar plastic zones in these materials. Finally, this provides guidance for mechanical models of tableting, machining, and property assessment of molecular crystals.
Taw, Matthew R., et al. "The mechanical properties of as-grown noncubic organic molecular crystals assessed by nanoindentation." Journal of Materials Research, vol. 32, no. 14, Jun. 2017. https://doi.org/10.1557/jmr.2017.219
Taw, Matthew R., Yeager, John D., Hooks, Daniel E., Carvajal, Teresa M., & Bahr, David F. (2017). The mechanical properties of as-grown noncubic organic molecular crystals assessed by nanoindentation. Journal of Materials Research, 32(14). https://doi.org/10.1557/jmr.2017.219
Taw, Matthew R., Yeager, John D., Hooks, Daniel E., et al., "The mechanical properties of as-grown noncubic organic molecular crystals assessed by nanoindentation," Journal of Materials Research 32, no. 14 (2017), https://doi.org/10.1557/jmr.2017.219
@article{osti_1369202,
author = {Taw, Matthew R. and Yeager, John D. and Hooks, Daniel E. and Carvajal, Teresa M. and Bahr, David F.},
title = {The mechanical properties of as-grown noncubic organic molecular crystals assessed by nanoindentation},
annote = {Organic molecular crystals are often noncubic and contain significant steric hindrance within their structure to resist dislocation motion. Plastic deformation in these systems can be imparted during processing (tableting and comminution of powders), and the defect density impacts subsequent properties and performance. This paper measured the elastic and plastic properties of representative monoclinic, orthorhombic, and triclinic molecular crystalline structures using nanoindentation of as-grown sub-mm single crystals. The variation in modulus due to in-plane rotational orientation, relative to a Berkovich tip, was approximately equal to the variation of a given crystal at a fixed orientation. The onset of plasticity occurs consistently at shear stresses between 1 and 5% of the elastic modulus in all three crystal systems, and the hardness to modulus ratio suggests conventional Berkovich tips do not generate fully self-similar plastic zones in these materials. Finally, this provides guidance for mechanical models of tableting, machining, and property assessment of molecular crystals.},
doi = {10.1557/jmr.2017.219},
url = {https://www.osti.gov/biblio/1369202},
journal = {Journal of Materials Research},
issn = {ISSN 0884-2914},
number = {14},
volume = {32},
place = {United States},
publisher = {Materials Research Society},
year = {2017},
month = {06}}
The tenth American Physical Society topical conference on shock compression of condensed matter, AIP Conference Proceedingshttps://doi.org/10.1063/1.55666