Ewald, Peter

Peter Paul Ewald (1888-1985) uses reciprocal lattice vectors to interpret the diffraction patterns by orthorhombic crystals and later generalized the approach to any crystal class. 

The sums may be carried out with respect to the atomic positions in direct (real) space or to lattice planes in reciprocal space, an approach introduced in 1913 by Paul Peter Ewald (1888-1985), a doctoral student under Arnold Sommerfeld (Ewald, 1913). In reciprocal space, the structures of crystals are described using vectors that are defined as the reciprocals of the interplanar perpendicular distances between sets of lattice planes with Miller indices (hkl). In 1918, Erwin Rudolf Madelung (1881-1972) invoked both types of summations for calculating the electrostatic energy of NaCl (Madelung, 1918). 

Peter Paul Ewald (1888-1985). German physicist, whose work [P.P. Ewald, Das reziproke Gitter in der Strukturtheorie, Z. Kristallogr. 56, 129 (1921)] is considered a landmark in using reciproeal lattice in x-ray diffraction. 

Max von Laue was a Privatdozent and Paul Peter Ewald was a doctoral student at the University of Munich in 1912 when Ewald told Laue about his thesis on crystal modek. In what he later called the bluest mistake of hk scientific fife, Ewald did not realize that the spacings between layers of hk model su ested the possibility of X-ray diffiaction, which Laue quickly went on to discover and prove. 

Adolf Kussmaul s Strassburg clinic, found that the gastric contents of one patient with pernicious anemia contained no hydrochloric acid. The fact that achlorhydria appears in patients destined to have pernicious anemia long before their anemia is recognized was repeatedly observed. In fact, Castle s older Boston confrere, Samuel Levine, in a study begun in 1915 at the Peter Bent Brigham Hospital, had found that of 148 consecutively studied patients with pernicious anemia, only 1 had a trace of acid in a Ewald meal recovered at the end of an hour. In three otherwise normal anacidic patients, pernicious anemia developed later. 

---