“In 1938,” she began, “a chemist at Dow Chemical named Dr. J. D. Hanawalt had a problem. X-ray diffraction was new and powerful. You shine X-rays at a crystal, the atoms inside act like a maze, and the X-rays bounce off the atomic planes, creating a unique fingerprint of peaks. Every mineral, every ceramic, every pharmaceutical compound—it has a unique pattern. But Hanawalt had thousands of patterns and no way to find a match.
“Exactly,” Elara smiled. “And you’d never have found it with the old cards. But the JCPDS’s legacy is why you can. Because someone, somewhere, took pure meridianiite, ground it up, put it in a diffractometer, measured every peak to a precision of 0.01 degrees, and sent that data to the ICDD.” jcpds xrd
So, he and a group of scientists founded the Joint Committee on Chemical Analysis by X-Ray Diffraction Methods . The JCPDS. Their mission was impossibly boring and impossibly heroic: they would measure pure, known compounds, one by one, and file their patterns on index cards.” “In 1938,” she began, “a chemist at Dow
She pointed to Leo’s failed pattern. “Your pattern has a strong peak at 12.1 degrees 2θ. That’s a large d-spacing—big atomic planes. That suggests a clay or an organic-inorganic hybrid. But the PDF-2 you searched is old. You need the full PDF-4+.” Hanawalt had a problem
And the library of dust grew by one more peak.