Researchers have found evidence of atomic-scale defect formation during crystal growth from the supercooled liquid. Researchers have long speculated that defects incorporate during growth, but until now had no evidence because they heal before they can be observed. Using high energy, high resolution in situ X-ray diffraction at the U.S. Department of Energy’s Advanced Photon Source, researchers overcame accuracy and data collection speed issues to make this discovery. The researchers found evidence of defects that involve swapping of the locations of the elements in Zr2Cu. In these antisite defects, some zirconium atoms swap places with copper. As a result, the length of the crystal unit cell decreases during growth while the width increases. Computer simulations confirmed that, because zirconium atoms are larger than copper atoms, only 1 to 2% of these defects are necessary to cause these distortions in the unit cell during crystal growth; the faster the growth rate, the more defects. This work provides a foundation for better understanding how to control material properties that are dependent upon defects created during solidification.
- M. J. Kramer, M. I. Mendelev, and R. E. Napolitano. In Situ Observation of Antisite Defect Formation during Crystal Growth. Phys. Rev. Lett. 105, 245501, (2010) DOI: 10.1103/PhysRevLett.105.245501