# Showing papers in "Advances in Physics in 1961"

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TL;DR: The van der Waals forces refer to the attractive forces acting between any two neutral atoms or molecules that are separated by distance large compared to their own dimensions, which decrease with distance according to a power law as mentioned in this paper.

Abstract: Publisher Summary The van der Waals forces refer to the attractive forces acting between any two neutral atoms or molecules that are separated by distance large compared to their own dimensions. These forces are of a long-range nature, which decrease with distance according to a power law. The basic idea of the theory is that the interaction between the bodies is considered to take place through a fluctuating electromagnetic field. This field is always present in the interior of a material medium and it also extends beyond its boundaries because of the thermodynamic fluctuations. Any change in the electrical proper ties of the medium in a certain region will, by Maxwell's equations, lead to a change in the fluctuation field that extends beyond that region. Therefore, the part of the free energy that is related to electromagnetic fluctuations is not determined by the properties of the substance solely at the point considered.

1,333 citations

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TL;DR: In this article, the theory of impurity conduction was introduced and the following conclusions were drawn: 1) impurity can be inferred from impurity, and 2) impur-ture conduction can be predicted.

Abstract: (1961). The theory of impurity conduction. Advances in Physics: Vol. 10, No. 38, pp. 107-163.

1,170 citations

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TL;DR: In this article, the anomalous temperature dependence of certain dielectric, piezoelectric and elastic constants in the paraelectric phase of ferroelectric crystals can be described and correlated in a very natural way in terms of crystal stability.

Abstract: In Part I the dielectric properties of cubic crystals with atoms in special positions were discussed, with particular reference to crystals which become unstable against a transverse optic mode of vibration of long wavelength. These considerations are now extended to crystals of general symmetry, and it is shown that the anomalous temperature dependence of certain dielectric, piezoelectric, and elastic constants in the paraelectric phase of ferroelectric crystals can be described and correlated in a very natural way in terms of crystal stability. A formula relating the dispersion frequency of the anomalous dielectric constant to the spontaneous polarization and the displacements of the atoms in a ferroelectric transition, previously derived for barium titanate, is generalized. The transitions in KH2PO4 and in NH4H2PO4, and the ordering of the hydrogen atoms in these crystals, are discussed qualitatively in terms of the stability of normal modes of vibration.

239 citations

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TL;DR: In this article, the shape of the Fermi surface is made to depend on a single parameter which can be interpreted as the pseudo-potential of the {111} atomic planes acting on an orthogonalized plane wave, giving rise to an energy gap of 5-10 ev at the zone boundaries.

Abstract: The Fermi Surfaces in Cu, Ag and Au are now known to be greatly distorted, with thick ‘necks’ passing through the zone boundaries. In this paper we enquire whether such an electronic structure is quantitatively consistent with the observed transport coefficients. The mathematical model is quite simple; the shape of the Fermi surface is made to depend on a single parameter which can be interpreted as the pseudo-potential of the {111} atomic planes acting on an orthogonalized plane wave, giving rise to an energy gap of 5–10 ev at the zone boundaries. Various integrals over the Fermi surface can then be evaluated by elementary methods, and compared with the corresponding experimental quantities. The electronic specific heat and optical mass in the pure metals are consistent with the model. The galvanomagnetic effects are shown to depend a great deal on the anisotropy of the electron relaxation time, whose variation with energy is also probably the electron relaxation time, whose variation with energ...

165 citations

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TL;DR: In this paper, the methods of measuring Debye temperatures and comparison of results for some cubic crystals were presented, and the results were compared with the results of some cubic crystal types.

Abstract: (1961). Methods of measuring Debye temperatures and comparison of results for some cubic crystals. Advances in Physics: Vol. 10, No. 40, pp. 313-355.

98 citations

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TL;DR: The theory of the interaction of electrons with lattice vibrations in metals was introduced in this article, where it was shown that electrons can interact with the lattice of metal lattices.

Abstract: (1961). The theory of the interaction of electrons with lattice vibrations in metals. Advances in Physics: Vol. 10, No. 40, pp. 357-400.

45 citations

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31 citations

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CERN

^{1}TL;DR: In this paper, the present position of theories of nuclear matter initiated some years ago mainly by Jastrow and Brueckner is discussed, and the difficulties encountered by the latter approach and their partial resolution by ideas from superconductivity theory are analysed.

Abstract: This article is an account of the present position of theories of nuclear matter initiated some years ago mainly by Jastrow and Brueckner. Section 1 introduces the basic ideas. Section 2 discusses the variational approach. Section 3 develops methods involving partial summations in perturbation theory. The difficulties confronting the latter approach, and their partial resolution by ideas from superconductivity theory, are analysed in § 4. Much of the formalism is relevant also in the theory of individual nuclei (see for example the review by Eden 1959) and in fields other than nuclear physics (see for example The Many Body Problem, Les Houches, 1958). However, in the selection of material our criterion has been relevance for the ground state of nuclear matter.

24 citations