Starting from a pseudopotential calculation for metallic beryllium the K-emission spectra of different polarizations, the Compton profiles for several directions, and the APS are calculated. Besides the shape of the emission spectra also the absolute values of the intensity are highly anisotropic due to the existence of localized charges along the hexagonal axis of Be. The calculated spectra agree well with a recently published measurement. The Compton profiles for three directions are Calculated in momentum approximation. The comparison of the anisotropies obtained with those of several measurements and a LCAO calculation shows a good conklation.Ausgehend von einer Pseudopotentialrechnung fur metallisches Beryllium werden die K-Emissionsspektren verschiedener Polarisationen, die Comptonprofile unterschiedlicher Richtungen sowie das AP-Spektrum berechnet. Neben der Form der Emissionsspektren ist auch die Absolutintensitiit wegen der Existenz lokalisierter Ladungen in Richtung der ~-~4 c h s e im Be stark anisotrop. Die berechneten Spektreii stehen im Einklang mit einer kurzlich veroffentlichten Messung. Die Comptonprofile werden fur drei Richtungen in Impulsniiherung berechnet. Der Vergleich der Anisotropien mit verschiedenen Messungen und einer LCAO-Rechnung zeigt eine sehr gute Ubereinstimmung. IntroductionBeryllium has some anomalous properties, for example, high Debye and melting temperatures, sound velocity, diamagnetic susceptibility, and electronic specific heat. Therefore, it has been the subject of many theoretical and experimental investigations during the last few years.Not only because of its properties but also due to its simple crystal structure (h.c.p.) and its atomic electron configuration there exist a lot of band-structure calculations.We intended to investigate spectroscopic properties of Be, closely connected to the band structure, by computing X-ray spectra and Compton profiles from the band structure and then comparing them with the experimental results.I n Section 2, X-ray emission spectra of single crystals are given. The K-emission spectrum of simple metals such as Be does not show significant peaks. Contrary to this, the polarized K-spectra of Be give far more information. Dropping the energy dependence of the matrix elements, such a polarized spectrum reflects the partial density of the occupied states of a certain magnetic quantum number.I n order to check the region above the Fermi level, we calculated the self-convolution of the unoccupied total density of states and compared this with an experimental AP spectrum in Section 3.Finally, in Section 4 the theoretical momentum distribution of single crystals is compared with Compton profiles for different directions of the scattering wave vector.The starting point of our calculations is the band structure of Be obtained by Taut [1]. From this calculation the energy values and the wave functions of the first 30 bands were available at a mesh of 222 points in 1/24 part of the Brillouin zone.
In the last years the reflection electron-energy loss spectroscopy (FELS) became a powerful tool in investigations of electronic excitations of the surface and the bulk of solids /1 to 4/. By energy variation of the primary electron beam bulk and surface excitations may be distinguished. A number of papers dealt with the changes in the characteristic loss spectra upon adsorption of gases /5 to 7/. 1)Especially the interest in the 3d transition metals increased in the last decade because of the complex nature of the information in RELS. Besides Cu /8, 9/ and Zn /lo/, spectra appeared for the clean surfaces of Ni /5 to 7/, F e /ll/, and V, Cr, T i /12/. We measured the RELS for polycrystalline C r and C r (100) Increasing the energy of the primary electrons the loss peak C rises whereas B is diminished. The loss maximum A vanishes for primary energy E > 300 eV.The peaks (D, E) and F a r e the well-known 3p and 3s ionization losses, respectively /3, 17, 2 3 , ' . From the behaviour of peaks B and C one may conclude that 1) Mommsenstr. 13, DDR. 4 physica (b)
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