Scientists Puzzled by ‘Rule of Four’ Pattern Found in Most Materials

A bizarre “Rule of Four” has been identified in the basic structure of the majority of inorganic materials—and scientists are stumped as to why.The pattern is found in the so-called “unit cell” of the materials—the smallest possible repeating part of each molecular structure.Researchers at the Swiss Federal Institute of Technology in Lausanne (EPFL) analyzed two massive databases that record the structural patterns of more than 80,000 known and predicted materials. They were surprised to discover that some 60 percent of materials had a unit cell in which the total number of atoms was a…