N. F. Mott N(E) s-band FIGURE 2. Proposed density of states in nickel(from Mott Jones, (%)p. 192. model took a long time to gain recognition. a ferromagnet that could be described in this way came to be called an'itinerant ferromagnet,. I think there was some conflict in the development of ideas between this concept and those who tried to reconcile it with the concept of localized moments, for instance by describing nickel as a mixture of states with the configurations 3d 10, 3d9 48l and 3d8 482 J. C. Lateran) in his Scientific biography (p. 191)makes the remark that in studying the work of Mott and Jones one got the impression that they felt that the potential actually occurring in the energy band theory was a small one, which could be handled by perturbation theory; and this affected the thinking of the English school of physicists so that even now [1976] they are trying to get valid results relating to energy-band theory from simplified models. , This perhaps refers to pseudopotential theory. But as regards our work in 1933-6, we were very much impressed by the work of wigner Seitz/(1a)in obtaining exact wavefunctions yo for the ground state of metallic sodium, and by the fact that, except near the nucleus, they were flat. Also we used the approximation yl=ekzy o for other k values. It was this fatness that led us to think that the free electron approximation might be a good one, except of course for d-bands. Whether this influenced 'the English schoolI am unable to say. Slater, of course, was the real leader in the use of computers, as they developed, to calculate energy bands by using exact wavefunctions, and in particular in including the effect of correlation In 1933, Klaus Fuchst came to Bristol, as a political refugee from Nazi germany. t Fuchs later worked in Los Alamos, and after the war as head of the theoretical group at Harwell. He was convicted in 1950 for communicating secret material to the Russians, and imprisoned for 9 years