Howard Flack

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Howard Flack

Howard Flack (born August 27, 1943 - † February 2, 2017 ) was a British chemist and crystallographer who spent most of his professional life in Switzerland. The focus of Flack's work was on the development of computer algorithms for crystallographic calculations and the use of the Internet for the exchange of crystallographic data. He became known through the Flack parameter for determining the absolute structure in the context of a crystal structure analysis .

education and study

Flack studied chemistry at the University of Nottingham from 1962 to 1965 . From 1965 to 1968 he wrote his dissertation Studies of Disorder in Anthrone and in Mixed Crystals of Anthrone-Anthraquinone at University College London under the direction of Kathleen Lonsdale .

Scientific work

After completing his dissertation, Flack accepted an assistantship in Cambridge. There he wrote his first contribution to pseudosymmetry in crystals. In 1972 he was appointed assistant professor at the Laboratoire de Cristallographie at the University of Geneva, where he worked with brief interruptions until his retirement in 2008. During his work in Geneva he contributed to the establishment of crystallographic laboratories at the universities of Lausanne, Neuchâtel (Switzerland) and Basel. At the same time he wrote parts of the program X-RAY 76. He also turned his attention to the problem of absorption corrections, which represent an important elimination of systematic errors in X-ray diffraction data. Since the existing algorithms were unsatisfactory, he developed a new algorithm. This algorithm was implemented in the CAMEL JOCKEY program. An extension was launched as CAMEL JOCKEY WITH THREE HUMPS , which was compatible with the X-RAY 76 program. His best-known contribution to applied crystallography dealt with the determination of absolute structures, i.e. the phenomenon that certain crystal structures can appear in two mirror-image variants. This applies, among other things, to crystals of all enantiomerically pure, chiral compounds. Crystals of the two variants of a compound show only slight differences in their X-ray diffraction intensities. Flack defined an algorithm for calculating a parameter which in many cases enables the correct structure to be identified. The calculation of the Flack parameter is one of the standard methods of determining crystal structure today. This also contributed to the fact that X-ray crystallographic methods became part of the standard analytical repertoire in the pharmaceutical industry.

Flack was a pioneer in the use of modern communication tools to disseminate and share crystallographic data. As early as 1992 he began dividing crystallographic data via email, telnot and gopher. In 1997 he became chairman of the Committee on Electronic Publishing, Dissemination and Storage of Information of the International Union of Crystallography . There he operated, among other things, the digitization of all editions of Acta Crystallographica and their publication on the Internet. Acta Crystallographica was one of the first specialist journals, all issues of which were accessible on the Internet. He was also a co-author of the 6th edition of the International Tables for Crystallography .

Teaching

From 1996 to 2009, Flack led a course in Computational Methods in Crystallography at the University of Geneva. From 2001 to 2003 he taught crystallography at the University of Lausanne on behalf of Dieter Schwarzenbach .

Honors

  • Price of the Lion Club in Geneva for original research (1980)

Private

Howard Flack married Evelyne Arn in 1972. The couple had two children. Flack learned to speak French fluently, but remained a British citizen until the end of his life.

Individual evidence

  1. ↑ HD Flack: Calculation of dimensions of ordered regions in triclinic and monclinic pseudosymmetric crystals from the intensity of diffuse scattering. In: Philos. Trans. R. Soc. London Ser. A , 266, 1970, pp. 575-582.
  2. ↑ HD Flack: Automatic absorption correction using intensity measurements from azimuthal scans. In: Acta Crystallographica , A30, 1974, pp. 569-573, doi: 10.1107 / S0567739474001343 .
  3. ↑ HD Flack: On enantiomorph-polarity estimation. In: Acta Crystallographica , A39, 876-881, doi: 10.1107 / S0108767383001762 .

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personal data
SURNAME Flack, Howard
BRIEF DESCRIPTION British-Swiss chemist and crystallographer
DATE OF BIRTH August 27, 1943
DATE OF DEATH 2nd February 2017