Zachariasen, William

Zachariasen, William Houlder was born in 1906. He was a Norwegian-American physicist who spent most of his career working in X-ray crystallography. His description of the glass structure in the early 1930s became a standard. He died in 1979. 

Work on direct methods was continued independently by Jerome Karle and Herbert Hauptman, ° Joseph Gillis, William H. Zachariasen, David Sayre, William Cochran, and Isabella Karle. Phase relationships were clearly found for the crystal structure of deca-borane (which is centrosymmetric), but were not so clear for some other structures. Gillis showed, however, that often certain inequalities were nearly satisfied, and this observation led to subsequent investigations of the probability relationships among the structure factors. Karle and Hauptman went on to show how the use of inequalities can restrict the range of phase angles for non centrosymmetric structures.. All of these studies led to the direct methods now used routinely in small-molecule crystallographic laboratories. 

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