M. Hargittai, I. Hargittai - Symmetry through the Eyes of a Chemist (793765), страница 79
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John Ruskin’s words are quoted here after L. V. Azaroff, Introduction toSolids. McGraw-Hill, 1960.158. C. Bunn, Crystals: Their Role in Nature and Science. Academic Press,New York, 1964.159. Ibid.EpilogueAt the end of our journey with symmetry in chemistry, we may ask thequestion whether there is any specific chemical symmetry.
Becauseof its unifying nature, the answer should be that there is only onesymmetry concept. Yet there are different emphases in different fields.In chemistry, we are seeking more the presence of symmetry whereasin physics, the stress on symmetry breaking appears more manifested. Crystals, for example, are often used in physics to demonstratesymmetry breaking. This is understandable if we imagine ourselves toshrink to the atomic size. In this case our wandering inside the crystalgives us the impression of broken symmetry.
For a chemist thoughthe regularity of a crystal projects perfect symmetry. Thus, we have totake the scale into account when judging the presence or absence ofsymmetry.Another consideration is the extent that determines the effect onwhose basis we judge a property. Even the most extended monocrystalis finite hence cannot be considered infinite to satisfy the requirementof space-group symmetry.
For an X-ray diffraction pattern though,whose existence testifies to its symmetry, the crystal needs to bemerely large enough to produce such a pattern. Thus the infinitycriteria can be fulfilled even within finite domains.There is then the interesting question whether symmetry can bequantified or not? There have been elaborate and bona fide attemptsfor such quantification and quantitative comparisons.
Their successis limited though because such questions can only be answered forspecific features but usually not in a general sense.Returning to the question whether chemical and physical symmetries may be different, there is, again, a difference in current research.In the physics of fundamental particles, the quest is still going on for505506Epilogueuncovering the most fundamental level of the organization of matterand finding the most universal level of symmetry.
In chemistry, thequest is more for the enhanced utilization of the already familiarsymmetries in areas of chemistry where they heretofore have not yetfound application. A shining example of success was the introduction of symmetry considerations in predicting the feasibility of chemical reactions. Current studies are aiming at explaining and predictingstructural differences between gaseous and crystalline structures andpredicting and explaining different preferences of different substancesfor crystallization. Further successes may occur in areas that we mightnot even be thinking of yet as the next ones in the utilization of thesymmetry concept.
Symmetry has been a most fruitful concept inchemistry in understanding our science and making it more powerful.It has also enhanced our pleasures in doing chemistry and connectingit with other human endeavors.In conclusion, we would like to stress that while symmetry is veryimportant in chemistry, it is only an ingredient.
There is no chemistrywithout the substances and their reactions and the separation of theproducts, and so on. We have to bear this in mind even when we areindulging in the symmetry aspects of our science.Other Titles by the AuthorsM. Hargittai, I. Hargittai, Visual Symmetry. World Scientific, Singapore,2008.I. Hargittai, The DNA Doctor: Candid Conversations with James D. Watson.World Scientific, Singapore, 2007.I. Hargittai, The Martians of Science: Five Physicists Who Changed theTwentieth Century. Oxford University Press, New York, 2006 (soft cover,2008).I. Hargittai, Our Lives: Encounters of a Scientist. Akadémiai Kiadó,Budapest, 2004.
German translation: Wege zur Wissenschaft, Lj-Verlag,Merzhausen, Germany, 2006.M. Hargittai, I. Hargittai, Képes szimmetria (in Hungarian, PictorialSymmetry), Galenus, Budapest, 2004.I. Hargittai, The Road to Stockholm: Nobel Prizes, Science, and Scientists.Oxford University Press, Oxford, 2002 (soft cover, 2003).
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