scholarly journals Fermi Radii of Lithium by Positron Annihilation

1971 ◽  
Vol 49 (24) ◽  
pp. 3227-3233 ◽  
Author(s):  
J. J. Paciga ◽  
D. Llewelyn Williams
Keyword(s):  
Fermi Surface ◽  
Positron Annihilation ◽  
Wave Functions ◽  
Scattering Data ◽  
Electron Wave ◽  
A Value ◽  
Band Structure Calculations ◽  
Detector Geometry ◽  
Point Detector ◽  
Structure Calculations

A collinear-point detector geometry has been used to study positron annihilation in single-crystal lithium. The results are interpreted in terms of the higher momentum components of the electron wave functions and the lithium Fermi surface. A consistent interpretation favors a value for the Fourier component V110 of the lattice potential of close to 0.10 Ry and a Fermi surface whose radius in the [110] direction is 2.9% greater than in the [100] direction. This latter result is consistent with Compton-scattering data and both results are in close agreement with the recent band-structure calculations of Rudge.

The dependence of the hyperfine interaction on the cellular potential in Na and K. II

1969 ◽  
Vol 47 (13) ◽  
pp. 1331-1336 ◽  
Author(s):  
R. A. Moore ◽  
S. H. Vosko
Keyword(s):  
Fermi Surface ◽  
Electron Density ◽  
Wave Functions ◽  
Electron Wave ◽  
Surface Electron ◽  
Conduction Electrons ◽  
Hartree Fock ◽  
A Value ◽  
Dependent Potential ◽  
Conduction Electron Density

The dependence of the Fermi surface electron wave functions in Na and K on (i) an L-dependent effective local cellular potential constructed to simulate Hartree-Fock theory and (ii) the inclusion of the Hartree field due to the conduction electrons in the cellular potential is investigated. All calculations are performed using the Wigner–Seitz spherical cellular approximation and the Schrödinger equation is solved by the Kohn variational method. It is found that to ensure a value of the Fermi surface electron density at the nucleus accurate to ~5%, it is necessary to use the L-dependent potential along with the Hartree field due to a realistic conduction electron density.

scholarly journals Fermi surface of the skutterudite CoSb3 : Quantum oscillations and band-structure calculations

2021 ◽  
Vol 103 (8) ◽  
Author(s):  
M. Naumann ◽  
P. Mokhtari ◽  
Z. Medvecka ◽  
F. Arnold ◽  
M. Pillaca ◽  
...  
Keyword(s):  
Band Structure ◽  
Fermi Surface ◽  
Quantum Oscillations ◽  
Band Structure Calculations ◽  
Structure Calculations

Experimental uniaxial stress and strain derivatives of the Fermi surface of rhenium

1980 ◽  
Vol 58 (8) ◽  
pp. 1191-1199 ◽  
Author(s):  
E. Fawcett ◽  
F. W. Holroyd ◽  
J. M. Perz
Keyword(s):  
Fermi Surface ◽  
Uniaxial Stress ◽  
Stress And Strain ◽  
Strong Anisotropy ◽  
Quantum Oscillations ◽  
Band Structure Calculations ◽  
Landau Quantum ◽  
Derivatives Of ◽  
Structure Calculations ◽  
The Magnetic Field

The derivatives of the areas of extremal orbits on all the small sheets of the Fermi surface of rhenium, with respect to stress and strain along the hexad axis, have been determined from simultaneous measurements of Landau quantum oscillations in magnetostriction and torque, and also in sound velocity and torque. Strong anisotropy is observed in the stress derivatives of orbits in zones five and six as the direction of the magnetic field defining the normal to the orbit is varied; the anisotropy is most pronounced for orbits which come close to the line of degeneracy AL on the hexagonal Brillouin zone face. The derivatives of the small void in zone eight are found to be very large; this is consistent with the results of band structure calculations which show that this feature of the Fermi surface is very sensitive to small changes in the Fermi energy. Cyclotron effective masses for a number of orbits on the void have also been measured.

The Fermi surface of caesium

1965 ◽  
Vol 287 (1408) ◽  
pp. 89-104 ◽  
Keyword(s):  
Fermi Surface ◽  
Signal Strength ◽  
Field Method ◽  
Orientation Dependence ◽  
Landau Levels ◽  
Harmonic Series ◽  
Spin Splitting ◽  
Experimental Conditions ◽  
Band Structure Calculations ◽  
Structure Calculations

A study of the de Haas-Van Alphen effect in caesium by the pulsed field method, under carefully controlled experimental conditions, has yielded information about the orientation dependence of the Fermi surface cross-section. A computer analysis of the results in terms of cubic harmonic series has indicated a probable radial distortion of some +3.3% in the [110] direction, — 0.9 % in the [100] direction, and — 1.4 % in the [111] direction; this is compared with the predictions of band structure calculations which, though indicating approximately the correct shape of Fermi surface, are appreciably in error as to the magnitude of the deviations from a sphere. The observed Fermi surface distortion is also discussed in terms of its effect on the low temperature thermoelectric power of caesium. The volume of the Fermi surface is found to be within a few tenths of 1 % of that calculated from published lattice constant data. Strong variations of signal strength with orientation were observed; these have been attributed in part to the effect of spin-splitting of the Landau levels.

The Fermi surface of beryllium

1964 ◽  
Vol 282 (1391) ◽  
pp. 521-546 ◽  
Keyword(s):  
Band Structure ◽  
Fermi Surface ◽  
Cross Section ◽  
Brillouin Zone ◽  
Field Direction ◽  
Pulsed Magnetic Fields ◽  
Hexagonal Symmetry ◽  
Band Structure Calculations ◽  
Structure Calculations ◽  
Good Agreement

The Fermi surface of beryllium has been determined experimentally by studying the de Haas–van Alphen effect of single crystals in pulsed magnetic fields. The de Haas–van Alphen frequency (proportional to the extremal area of the Fermi surface normal to the field) was measured as a function of field direction. Consideration of the hexagonal symmetry of the Brillouin zone (discussed in the Appendix) shows that only six distinct classes of fre­quency variation with field direction are possible, and these considerations are used to deduce the locations and forms of the various sheets of the Fermi surface. The Fermi surface is found to consist of hole and electron surfaces of equal volume (each containing 0∙162 carrier per atom). The hole surface is somewhat like a coronet, i. e. a ring of six smoothed tetrahedra joined by small necks lying in the central (0001) plane of the first double Brillouin zone, and the electron surface is a set of six roughly ellipsoidal surfaces (cigars) lying on the vertical edges of the second double zone. Detailed shapes and sizes are deduced for the coronet and cigars such that the extremal areas of cross-section are consistent to within 1 % of those obtained from the observed de Haas–van Alphen frequencies. No oscillations of frequency corresponding to the outer (0001) orbit round the coronet were, however, observed; a study of the field dependence of amplitude of the oscillations from the coupled orbit round the cigar shows that this absence can be explained by magnetic breakdown of the {101̄0} band gap. The model described is in good agreement with the predictions of recent band structure calculations, and is consistent with other experimental evidence.

Change of the de Haas – van Alphen frequency of potassium with pressure

1980 ◽  
Vol 58 (3) ◽  
pp. 370-375 ◽  
Author(s):  
Z. Altounian ◽  
W. R. Datars
Keyword(s):  
Band Structure ◽  
Fermi Surface ◽  
Pressure Dependence ◽  
Charge Density Wave ◽  
Energy Gap ◽  
Density Wave ◽  
Surface Anisotropy ◽  
Band Structure Calculations ◽  
Structure Calculations ◽  
Fermi Surface Anisotropy

The pressure dependence of the de Haas – van Alphen frequency in oriented potassium samples has been investigated with pressures up to 4.6 kbar. The change of frequency with pressure is less than that expected from free-electron scaling and the Fermi surface anisotropy increases from 0.13% at zero pressure to 0.47% at 4 kbar. These results are discussed in terms of band structure calculations and the charge density wave (CDW) model of potassium. The CDW energy gap changes with pressure for the CDW model to be applicable.

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