Obituary - John S. Kasper (1915 - 2005)

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John S. Kasper (1915 - 2005)

ACA RefleXions, Winter 2005

John Simon Kasper died peacefully on October 1, 2005 in Scotia NY. He was born in Newark, NJ on May 27, 1915, son of John F. Kasper and Josephine Naujalis Kasper. He earned his bachelor’s degree in Chemistry in 1937 and his PhD in 1941, both from the Johns Hopkins University. John taught chemistry for a year at Washington University in St. Louis, MO and then worked on the Manhattan Project at Columbia University until the end of World War II. In October, 1945 he joined the General Electric Research Laboratory in Schenectady, NY, and worked there and at the GE Research and Development Center until he retired in 1980, although he continued as a consultant for GE for several years after that.

John was a charter member and president of the ACA (in 1967, the year that ACA met in Atlanta and in Minneapolis). He was also on the USA organizing committee for the IUCr meeting in Stony Brook, NY in 1969. He edited, along with Kathleen Lonsdale, Volume II of the International Tables for X-ray Crystallography (Mathematical Tables).

Probably John’s most important contribution to crystallography was that in order to solve the structure of decaborane (B10H14) he thought of using Cauchy Inequalities to get around the “phase problem” which had baffled crystallographers for 50 years. The result was that he and David Harker derived “Harker-Kasper Inequalities” (see the following note by Jenny Glusker).

John’s research using x-ray diffraction spanned a wide range of materials: the structures of metals and intermetallic compounds, and unusual forms of many elements. Materials formed at very high pressures by Francis Bundy included artificially produced industrial diamonds that John was able to prove by their x-ray diffraction patterns to be true diamonds. Over a period of about 3 years John spent some time at the Brookhaven Laboratory using neutron diffraction to study antiferromagnetism. One of his great pleasures was that for many years he had graduate students working with him on their research projects. They were mostly from Rensselaer Polytechnic Institute in Troy, NY, but some also came from the State University of New York at Albany.

On leave from GE in 1957 he was a visiting professor at the University of Bristol, England, where he worked with F. Charles Frank on complex alloys and their closest packing. In 1975-76 he was visiting professor at the Université de Bordeaux, France, in the department headed by Paul Hagenmuller, working principally with Roger Naslain along with Michel Pouchard, Christian Cros, Jean Etourneau, Jean Michel Quinnisset and others in the study of composite materials. John’s collaboration with that group of French scientists continued from the mid 1960’s until the time that he retired. Patrick Cassoux of the Université de Toulouse, France, spent some months at GE and John enjoyed working with him.

John was a wonderful person with great patience and a twinkle in his eye and a great sense of humor. He delighted in his children and grandchildren. He played a social game of golf to relax and loved to play bridge. He was a good musician and continued to enjoy classical music even after his stroke approximately 10 years ago. Even after the stroke he retained some long term memory so that we were able to recall many happy past occasions

He is survived by his wife, Charlys Lucht Kasper, whom he married in 1951, his daughter, Marion O’Keefe and granddaughter Colleen O’Keefe, a son, Robert Kasper (wife Theresa), 3 grandsons; David, Daniel and Joseph Kasper, granddaughter, Colleen Belharrat, grandson, Timothy Kasper and 2 great grandsons. His older son, Frederick, died in 2000.

Charlys Kasper

Harker - Kasper Inequalities

John Kasper’s contribution to phase determination in x-ray diffraction studies is described in two important papers, both with his colleague David Harker and the second also with his future wife, Charlys Lucht. The main article entitled “Phases of Fourier Coefficients Directly from Crystal Diffraction Data” by D. Harker and J. S. Kasper (J. Chem. Phys. 15: 882-884, 1947; Acta Cryst. 1: 70-75, 1948) is short but very significant. The authors were at General Electric Company, Schenectady. New York. They pointed out that one can measure intensities but not relative phases of diffracted x-ray beams (the “phase problem”) but that they had found a way to help solve this problem. They used “unitary atomic-structure factors,” U_hkl = (F_hkl)/f, where F is a structure factor and f represents scattering factor(s). By application of “Cauchy’s inequality” they found |U_hkl|2 is less than or equal to unity. [Cauchy’s inequality is (Σab) ² < Σa² Σb², unless a and b are proportional to each other. The corresponding inequality for integrals is due to Schwarz and Buniakowsky.] Harker and Kasper showed that if the crystal has a center of symmetry then U_2h,2k,2l is probably positive or zero (phase angle of 0 degrees) if the absolute value of U_2hkl is greater than or equal to one half. Several other relationships arising from further symmetry were then identified by them. Harker-Kasper inequalities are considered to be based on the non-negativity of the electron-density function.

John described this discovery with Dave Harker as follows: “I became intrigued with the fact that the straightforward squaring of a real structure factor, F_hkl (with cosine terms) contained, in part, the sum of modified cosine squared terms. These latter could be rewritten, by virtue of the relation 2 cos²A=1+cos 2A as components of F_2h,2k,2l. A relation then exists between F_2hkl and F_2h,2k,2l, but also with the summation of cross terms. I did not know what to do with the cross terms and so I put the thing aside. Some days later (in 1947) it occurred to me that Schwarz’s inequality would deal only with the desirable summation of cosine² terms. Accordingly, one morning at work I wrote down the relationship between F_2hkl and F_2h,2k,2l resulting from the application of Schwarz’s inequality. No sooner had I written this down, when Dave walked in the office and looked over my shoulder. “What is that?” Dave asked. “That is the result of applying Schwarz’s inequality to a structure factor,” I replied. After satisfying himself that what I had written was correct, Dave became quite excited and remarked: “You can determine signs with that.” “That’s right,” I replied.” Charlys shared the excitement of the moment, writing: “It was an event one doesn’t forget.”

Dave suggested using the unitary atomic structure factor . This enabled treatment of more general situations. John continued “For the next few weeks Dave was immersed in the applications to various symmetries and space groups, and other ramifications, such as sum and difference formulas. He also produced an elegant write up of the work. I concentrated on its application to the Decaborane problem which was uppermost in our minds.”

The method was first applied to the crystal structure of decaborane, B₁₀H₁₄, a small molecule of unknown structural formula, space group Pnnm (J. S. Kasper, C. M. Lucht and D. Harker, "The Crystal Structure of Decaborane, B₁₀H₁₄." Acta Cryst. 3: 436-455 (1950)). Robinson Burbank described the work in his 1976 ACA past-presidential address. He had heard the report on the determination of the crystal structure of decaborane by Kasper, Lucht and Harker at a meeting in 1948 and wrote: “As luck would have it they had unknowingly chosen the most intractable problem in the entire field of boron hydrides. They had been bedeviled by micro twinning, high specimen volatility, and a host of other technical difficulties. More importantly, the entire structural concept of the boron hydrides was dead wrong! This meant that every conceivable model that might be postulated was doomed to failure. Finally, in desperation John turned back to the phase problem and in a moment of inspiration discovered that it was possible to deduce something about the signs of the structure factors using the Schwarz inequality. David pounced on this breakthrough and it was rapidly developed into the tool that solved the decaborane structure. The open clam shell configuration defined by an incompleted icosahedron is now in freshman chemistry books but until that paper, it had never penetrated the mind of man.” The authors derived many inequalities, based on symmetry elements of the space group of decaborane. In addition, it was necessary in several cases to add or subtract two U’s before applying Cauchy’s inequality (“addition-subtraction” relations). In the years that followed many crystallographers used Harker-Kasper inequalities to help solve structures until the now commonly used “direct methods”, partly inspired by this work, were developed.

Jenny Glusker