Prediction of properties of intermetallics using a chemical bonding model
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I. INTRODUCTION
IT is a pleasure to participate in this recognition of the importance of the work of Milt Blander. I wish to follow in his direction. Technology in the future will require a large variety of new materials with properties considerably different from present materials. The combination of 90 metals can produce an enormous variety of materials; however, to find the desired material by the Edisonian approach is impractical. We must have some means of predicting which compounds will meet the requirements of a new process. This predictive model is an extension of the Brewer– Engel theory. II. DISCUSSION To make it practical for the people making the new developments, they should have a rather simple procedure for predicting properties. The procedure that we are presenting can be evaluated using hand calculators and would require little time. To achieve this, one must have a model with a minimum number of parameters. An example of the value of reducing parameters and still maintaining desirable accuracy is the experience of Professor William Klemperer and his student, Alfred Buechler,[3] who were developing a model for calculating the stability of gaseous alkali halide molecules. The previously used model assumed point charges for each ion and yielded results close to the experimental values with that simple a model. Klemperer recognized that the ions will not be spherical and that one would have to take into account quadropolar, octopolar, and higher order polarizability terms. When these terms were taken into account, it was found that the more terms added, the poorer the results. Each one of the terms has a substantial uncertainty and, when added together, produces an uncertainty considerably larger than that of the point charge model. We are following LEO BREWER, Professor, is with the Department of Chemistry, University of California at Berkeley, Berkeley, CA 94720. This article is based on a presentation made at “The Milton Blander Symposium on Thermodynamic Predictions and Applications” at the TMS Annual Meeting in San Diego, California, on March 1–2, 1999, under the auspices of the TMS Extraction and Processing Division and the ASM Thermodynamics and Phase Equilibrium Committee. METALLURGICAL AND MATERIALS TRANSACTIONS B
the approach of restricting our terms to those that vary markedly across the Periodic Table and combining those terms that vary smoothly across the Periodic Table to minimize the number of parameters that we use. A common reaction to my use of a simple chemical bonding model is that the model cannot work. The negative reaction to a new method is described by Thomas S. Kuhn in his book.[4] I have had this experience with each of the novel approaches that I have introduced for the past 60 years. After a decade of confirmations, I have received an award for the success of the approach offered 10 years earlier. However, the use of a chemical bonding model for metals can be readily accepted by chemists. As an example, I received a letter from Linus Pauling several years ago with the foll
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