Bernd Matthias File

Date: January 16, 1968

Subject: Ferroelectric Substances

I talked today with Bernd Matthias about my memorandum of 2 January to him.

He said that he had investigated HCrC₂, hydrogen chromium (III) dioxide, and had found it not to be ferroelectric. I told him that neutron diffraction work by Walter Hamilton and Jim Ibers has shown that in the deuterium compound the hydrogen bonds are nearly or completely symmetrical, very short, about 2.49 Å , I think, but that in the hydrogen compound the bonds are unsymmetrical I said that his negative result might be the result of electrostatic repulsion of the protons. He and I developed the idea that a solid solution of the deuterium compound and the hydrogen compound might show ferroelectricity. He suggested the fifty: fifty compound, and I suggested the one third/two thirds compound as the more likely to be ferroelectric, on the basis of the idea that you can get a regular structure more easily in a triangular plane network with the latter ratio than with the former. I think that with the one: two ratio the deuterium atoms would move to one side, and the hydrogen atoms to the opposite side of the basal plane, giving a net moment.

He asked if I would be willing for the Bell Lab people to make some of the hydrogen hexacyanide compounds that I had mentioned in my note, and I gave my permission.

I pointed out that not only hexacyano cobaltic acid, but also salts of ferro-cyanic acid in which one of the four hydrogen atoms is replaced by a univalent cation and certain other compounds that might be predicted to be ferroelectric. He mentioned that these compounds that I had suggested for investigation in my 2 January letter represent a completely new class of substances, or would represent a new class of ferroelectric substances if they are found to be ferroelectric.

Linus Pauling