-
9
-
-
0002069481
-
-
edited by, J. T. Devreese, P. Van Camp, Plenum, New York
-
(1985)
Electronic Structure, Dynamics, and Quantum Structural Properties of Condensed Matter
, pp. 401
-
-
Bortolani, V.1
Franchini, A.2
Santoro, G.3
-
14
-
-
84927875314
-
-
Several attempts have been made to resolve this dilemma. One proposal was that the He intensities are overmphasized by a multiphonon background (Refs. 14 and 15). On the basis of recent advances in our understanding of multiphonon processes, this explanation can now be ruled out with considerable confidence (Ref. 16). It has also been implied that part of the problem may have to do with the different schemes used to fit the bulk data (Ref. 10). Both approaches are based on the Born–von Kármán parametrization of lattice forces but differ in the number of force-consatnt parameters considered. Although this might provide for uncertainties in the size of the effect obtained, there is general agreement that this cannot account for the large extent in the gross differences.
-
-
-
-
25
-
-
84912799085
-
Evidence for a Charge Density Wave Driven Reconstruction in W(001)
-
Additional evidence for the effect of electrons at surfaces on HAS comes from several recent experiments on, for example, W(001) [, ] and the layered compounds such as TaS2 [G. Benedek, G. Brusdeylins, F. Hofmann, P. Ruggerone, J. P. Toennies, and R. Vollmer (unpublished)]. There the diffraction intensities are found to depend crucially on small modulations in the surface electron density, which in the above examples result from change-density waves, superimposed on the otherwise very smooth surface electron density distributions. In both cases these effects are more important than even the modulations caused by the ion cores. The experiments on TaS2 indicate moreover that the phonon-induced modulation of the electron density provides the major coupling of the helium atoms to lattice vibrations.
-
(1989)
Europhysics Letters (EPL)
, vol.10
, pp. 747
-
-
Ernst, H.-J.1
Hulpke, E.2
Toennies, J.P.3
-
41
-
-
0000994202
-
-
edited by, W. Kress, F. W. de Wette, Springer Series of Surface Sciences Vol. 21, Springer, Berlin
-
(1991)
Surface Phonons
, pp. 111
-
-
Toennies, J.P.1
-
42
-
-
84927875311
-
-
Tables of the data points can be obtained by writing to J. P. Toennies.
-
-
-
-
47
-
-
84927875310
-
-
Recently, for all three Al low-index surfaces this procedure has been shown to yield a set of force constants in good agreement with a first-principles calculation: A Franchini, V. Bortolani, G. Santoro, V. Celli, A. G. Eguiluz, J. A. Gaspar, M. Gester, A. Lock, and J. P. Toennies (unpublished).
-
-
-
-
48
-
-
84927875309
-
-
The simple force-constant calculations for βppds= β1b and βparas= 0.85 βb carried out by N. Luo in our laboratory show that the longitudinal resonance is not shifted downwards enough to agree with its position observed both by EELS and HAS, contrary to what is implied in Ref. 10.
-
-
-
-
51
-
-
84927875307
-
-
The multiphonon background was not accounted for in the calculation of Fig. 4. Its effect would be to reduce the relative differences in the Rayleigh and longitudinal peak intensities by no more than 30% and thus does not have a significant effect.
-
-
-
-
54
-
-
84927875306
-
-
E. G. Brovman and Yu. M. Kagan, in Dynamical Properties of Solids, edited by G. K. Horton and A. A. Maradudin (North-Holland, Amsterdam, 1974), p. 191.
-
-
-
-
58
-
-
84927875304
-
-
A. Franchini, dissertation, University of Modena, 1985/86.
-
-
-
-
59
-
-
84927875303
-
-
The first-order He diffraction intensities along the langle 112 rangle azimuth relative to the specular peak are at incident energies of approx 30 meV (unless otherwise indicated): 1 times 10-3 for Ag(111) [G. Boato, P. Cantini, and R. Tatarek, in Proceedings of the Seventh International Vacuum Congress and Third International Conference on Solid Surfaces, Vienna, 1977, edited by R. Dobrozemsky, F. Rüdenauer, F. P. Viehböck, and A. Breth (Berger, Wien, 1977), Vol. 2, p. 1377;
-
-
-
-
61
-
-
84927875302
-
-
< 2 times 10-4 for Cu(111) (Ref. 6);
-
-
-
-
63
-
-
84927903449
-
-
and 1 times 10-3 for Pt(111) (Ref. 18). A ratio of 1 times 10-3 corresponds to a corrugation amplitude of between 2 times 10-3~ A ang (Ref. 19) and 2 times 10-2~ A ang [, ] depending on the computational method and model used to describe the atom-surface potential.
-
(1987)
Jonsson and Weare, Surf. Sci.
, vol.181
, pp. 495
-
-
-
69
-
-
84927875300
-
-
Despite several attempts, has not been possible to fit the longitudinal mode with a Born–von Kármán fit involving modified surface force constants: A Reichmuth (unpublished) and G. Santoro (private communication).
-
-
-
|
