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Correspondence

Letter from Linus Pauling to Louis Jordan. April 3, 1945.
Pauling writes to discuss the details of his work on metal alloys for use in hypervelocity guns.

Transcript

SECRET

April 3, 1945

AIR MAIL

Dr. Louis Jordan, Executive Officer

Research Board for National Security

2101 Constitution Avenue

Washington 25, D.C.

Dear Dr. Jordan:

I send herewith a brief reply to your letter of 27 March 1945. I am leaving in a few days for the East, where I shall attend the meeting on April 18 of the Research Board for National Security, and also take care of some other matters. I do not have time before leaving to prepare for you a detailed statement about the field of research referred to in your letter. If this brief reply to your letter is not satisfactory, please let me know, and I shall write a detailed and documented statement as soon as the available time allows.

The problem about the dynamic properties of materials is given in your letter as described by the Navy in the following terms:

"The fundamental relationship of the atomic structure of metals to their dynamic properties is an important study from the standpoint of producing metals having higher resistance to impact. This, in turn, is an essential item in the construction of superior instruments of warfare, particularly armor, projectiles, and guns where the rates of loading are far in excess of those normally encountered in the civilian use of metals. The subject of the interpretation of the physical properties of metals in terms of the atomic and electronic structure is a very important and difficult one on which relatively little progress has been made until quite recently. Now, however, the field is opening up and the interest amongst physicists and theoretical metallurgists is greatly on the increase. It is believed that the state of the civilian art and the attack on the problem by scientific groups will produce a great increase in our understanding of this field within the next 5 to 10 years. After such progress has been made, it might be well for RBNS to attack the specific problem, having direct military indication of interpreting the behavior of metals under very high rates of loading in terms of the fundamental knowledge which will have been accumulated by that time. This particular subject may not be adequately handled by the civilian art."

The opinion given in this statement agrees very closely with my own opinion. It is true that for many years very little progress was

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made in the correlation of the physical properties of metals with their composition and structure, but in recent years the development of the electronic theory of metal and the experimental determination of the atomic arrangement in crystals of metals, intermetallic compounds, and other alloys has led to striking progress. A satisfactory correlation between the physical properties of metals and alloys and the electronic and atomic structure of the material has not yet been made in general, but I believe that it can be expected that an intensive attack on this problem during the coming decade should provide very important results. There is in my opinion a good chance that ten years from now theoretical considerations based on electronic and atomic theory may be used as an aid in the formulation of alloys with physical properties superior to those of any material now available.

The United States is at present behind the European countries in cultivating this field of research. I recommend for the consideration of the Research Board for National Security the following suggestions:

1. An empirical attack, by the customary metallurgical and metallographical techniques, on the problem of formulating alloys with special properties necessary for certain applications for the national security, such as increased resistance to impact. I suggest that Dr. Zay Jeffries be asked to recommend the persons or agencies that could do this work best.

2. Attack on the problem of the relation between physical properties of metals and electronic structure. I suggest Dr. Frederick Seitz, Jr., Chairman of the Department of Physics of the Carnegie Institute of Technology, for this work.

3. The experimental investigation, with use of X-rays and other techniques, of the atomic arrangement in intermetallic compounds and solid solutions, and the theoretical study of the nature of the interatomic forces which find expression in the formation of intermetallic compounds. During the past fifteen years very extensive experimental investigations with X-rays of the structure of intermetallic compounds and other alloys have been made. This work has been done by Sir Lawrence Bragg, A.J. Bradley, and other investigators in England, A. Westgren, G. Phrgmen, and G. Hagg in Sweden, and a number of investigators in German. Very little work along these lines has been carried on in America. Although a great amount of information has been obtained, still more work remains to be done, and it is to be expected that further work will be of much greater practical importance than that which had already been carried out. It is to be regretted that no outstanding crystal structure investigator in this country is carrying on work in the field of metals. I think that it would be wise for the RENS to make some arrangements for first class work along these lines to be carried out in this country. Another field in which great fundamental progress may be made is that of the discovery of the nature of the forces determining the composition of intermetallic compounds. The gamma alloys in the brasses,

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bronzes, aluminum bronzes, and related systems illustrate the peculiar character of intermetallic compounds. All of these alloys are similar in their physical properties, but their chemical compositions are surpizingly [sic] different; representatives are CU5ZN8, CU9AL4, CU31SN8, and FE5ZN21. Other sets of intermetallic compounds with similar properties are also known, and a few regularities in their composition have been discerned. However, the general principles determining the composition and the choice of alternative structures by intermetallic compounds have not yet been formulated. the chemical theory of metals is at present in an embryonic state. The development of a sound fundamental theory of the chemistry of metals should lead to very important practical consequences.

Sincerely yours,

Linus Pauling

LP:fh

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