title: Anisotropic crystal deformation measurements determined using powder X-ray diffraction and a new in situ compression stage.
abstract: This report addresses the development of experimental and computational estimations of the anisotropic elastic moduli (EM) of single crystals to aid in the a priori (i.e., starting with the crystal structure) prediction of the trend as a function of the direction of applied stress. Experimentally EM values in the normal direction to the X-, Y- and Z-planes of block shaped aspirin and acetaminophen crystals were determined using data generated by the newly designed compression stage housed in our powder X-ray diffractometer. Computational estimations of EM were made using the applicable modules in Material Studio 5.5. The measured EM values normal to the (100), (020) and (002) planes of aspirin, and (20-1), (020) and (001) planes of acetaminophen crystals by both methods succeeded in detected the anisotropic behavior. However, disparity in the relative values between measured EM values by different techniques was observed. This may be attributed to deformation sources other than lattice compression including inelastic processes such as local failure and plasticity as well as deformation at the crystal-probe interfaces due to crystal surface roughness (asperities). The trend of the ratio of the values from the respective methods showed reasonable agreement and promise for the technique. The present approach demonstrated the suitability of the compression stage to determine and predict anisotropic EM of subjected small molecular organic crystals.
authors.affiliation: College of Pharmacy, University of Hawai'i at Hilo, 34 Rainbow Drive, Hilo, HI 96720, USA. rahulh@hawaii.edu
authors.forename: Rahul V
authors.initials: RV
authors.lastname: Haware
authors.forename: Paul
authors.initials: P
authors.lastname: Kim
authors.forename: Lauren
authors.initials: L
authors.lastname: Ruffino
authors.forename: Brian
authors.initials: B
authors.lastname: Nimi
authors.forename: Catherine
authors.initials: C
authors.lastname: Fadrowsky
authors.forename: Michael
authors.initials: M
authors.lastname: Doyle
authors.forename: Stephan X M
authors.initials: SX
authors.lastname: Boerrigter
authors.forename: Alberto
authors.initials: A
authors.lastname: Cuitino
authors.forename: Ken
authors.initials: K
authors.lastname: Morris
mesh_terms: D000082:Acetaminophen / Q000737:chemistry*; D016880:Anisotropy; D001241:Aspirin / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization; D006801:Humans; D033362:Powder Diffraction; D011312:Pressure; D014961:X-Ray Diffraction
chemical_list: D000082:Acetaminophen; D001241:Aspirin