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A study is made of the anisotropy of the properties of tungsten single crystals for equivalent crystallographic orientations relative to the growth axis. An essential difference in the interplanar spacings for samples with equivalent faces perpendicular and parallel to the growth axis was found. For the compared equivalent planes differences in the positron annihilation parameters were observed which point to an anisotropy of the Fermi surface caused by carbon atoms with an anisotropic electron configuration. The sublimation energy for equivalent faces is also shown to be anisotropic.

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A method is given for the investigation of momentum distribution of γ‐quantum annihilation from the metal surfaces. The method uses the interaction between positronium atoms and surface atoms. Possible mechanisms of this interaction are discussed and the conditions under which the method may be applied are defined. The method was used for the investigation of the momentum distribution of photon annihilation from the surface of polycrystalline iron and aluminium, and single‐crystalline molybdenum. It is shown that this distribution is parabolic for Fe and Al and differs significantly from the conduction electron distribution in the bulk metal. For Mo crystals it was concluded that there are two states for electrons on the surface of the (100) plane. It is assumed that the experimental definition of the electrons density gradient on the metal–vacuum interface may serve as a criterion which allows to estimate some physical properties of metal and alloy surfaces. The possibilities of the new method are disccussed.

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