Pepinsky and the X-RAC
As Wheeler Davey’s tenure as leader of the X-ray diffraction group came to an end with his retirement in 1949, other important faculty came to Penn State to lead X-ray diffraction into the second half of the 20th Century. One was Ray Pepinsky, who joined the Penn State faculty soon after Davey’s retirement. Pepinsky was a leading expert in the field of determination of structures, atomic locations, polarity, and bonding through detailed X-ray analysis. His work on radar in WWII and his interest in crystallography led to his invention of a machine that automatically calculated details of crystal structures. This machine, the X-Ray Analog Computer (X-RAC), attracted crystallographers from around the world to Penn State to have it shift through their X-ray data and create electron density maps indicating the nature of bonding within a structure. The X-RAC instrument was so popular among crystallographers and the scientific community at large that Life Magazine featured it in 1954.
Under Pepinsky’s famously hard-driving direction, his lab also discovered many new families and compositions of ferroelectrics and antiferroelectric materials. The details of the structural changes also led to insights into subtle ion displacements and dipolar ordering at the structural phase transitions of these ferroelectric and related materials. The Pepinsky group also gave important insights into biological crystal structures that included proteins, polypeptides, and other biological molecules. Their work led foremost scientists to visit Penn State, such as Helen McGraw of Cambridge and Gen Shirane of the Tokyo Institute of Technology. In addition, Pepinsky founded the Groth Institute for crystallography at Penn State, and conducted research for the CIA. Pepinsky left Penn State in 1959 but established Penn State’s reputation as a leader in crystal chemistry, ferroelectrics, and structural analysis that continues to this day.