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A planar approach to the lattice dynamics of polar semiconductor superlattices
A515 486
Surface Science 221 (1989) 486-512 North-Holland, Amsterdam
A PLANAR APPROACH TO THE LATrlCE DYNAMICS OF POLAR SEMICONDUCTOR SUPERLATI'ICES L MIGLIO Dlpartlmento dt Flstca dell" Unwersitd e Unit& G N S M - C I S M dl Mdano, vta Celorta 16, 1-20133 Mdano, Italy and L COLOMBO
*
Dtparttmento dt Flstca "A Volta" e Unitdt G N S M - C I S M dl Pavia, wa Basst 6, 1-27100 Pavta, Italy Received 5 April 19890 accepted for publication 24 April 1989 We present a planar approach to the calculation of the dynanncal matrix for polar semiconductor superlattlces m-plane and inter-plane Coulomblc force constants are derived analytmally Tins techmque obtains a fast convergence of the lattice summauons and allows for a helpful comparison between the analytic expressions of single slab force constants and superlattlce ones The ongm and the dispersive behavior of macroscopic Interface modes are &scussed m comparison to Fuchs and Khewer surface branches A numerical apphcatxon to the (GaAs)3(A1As)3 system is made m the framework of the bond-charge-model dynarmcs the sensmvlty of the rmcroscoplc mterface wbrations to the interface force constants parametnzatlon is pointed out by a few examples
Surface Science 221 (1989) 513-533 North-Holland, Amsterdam
bee A L K A L I REVISITED
513
METALS: BULK, SURFACE AND CHEMISO~ON THROUGH A MAGNETIC APPROACH
P a u l B L A I S E *, J e a n - P a u l M A L R I E U
and Daniel MAYNAU
Laboratotre de Phystque Quantlque, Unttd Assoctde (505) du Centre Nattonal de la Recherche Sctenttftque, UmversttJ Paul Sabatwr, 118 route de Narbonne, 31062 Toulouse Cedex, France Received 3 Apral 1989, accepted for publication 6 June 1989 A non-empirical Helsenberg Harmltoman denved from the L12 or Na 2 ab ~mtlo potential curves, is applied to surface problems of the alkah metals The process consists in the fourth order perturbation of a N6el state taken as zeroth order wavefunctlon Besides the bcc bulk characteristics, wluch are correctly reproduced, the relaxations on the (100) and (110) surfaces seem to be correctly reproduced (contractions of about 35~ and < 1% amphtude respectively) The method enables one to study the adsorption of an atom on the surface, the site and the strength of the binding as well as the activation energy for magration
Surface Science 221 (1989) 486-512 North-Holland, Amsterdam
A PLANAR APPROACH TO THE LATrlCE DYNAMICS OF POLAR SEMICONDUCTOR SUPERLATI'ICES L MIGLIO Dlpartlmento dt Flstca dell" Unwersitd e Unit& G N S M - C I S M dl Mdano, vta Celorta 16, 1-20133 Mdano, Italy and L COLOMBO
*
Dtparttmento dt Flstca "A Volta" e Unitdt G N S M - C I S M dl Pavia, wa Basst 6, 1-27100 Pavta, Italy Received 5 April 19890 accepted for publication 24 April 1989 We present a planar approach to the calculation of the dynanncal matrix for polar semiconductor superlattlces m-plane and inter-plane Coulomblc force constants are derived analytmally Tins techmque obtains a fast convergence of the lattice summauons and allows for a helpful comparison between the analytic expressions of single slab force constants and superlattlce ones The ongm and the dispersive behavior of macroscopic Interface modes are &scussed m comparison to Fuchs and Khewer surface branches A numerical apphcatxon to the (GaAs)3(A1As)3 system is made m the framework of the bond-charge-model dynarmcs the sensmvlty of the rmcroscoplc mterface wbrations to the interface force constants parametnzatlon is pointed out by a few examples
Surface Science 221 (1989) 513-533 North-Holland, Amsterdam
bee A L K A L I REVISITED
513
METALS: BULK, SURFACE AND CHEMISO~ON THROUGH A MAGNETIC APPROACH
P a u l B L A I S E *, J e a n - P a u l M A L R I E U
and Daniel MAYNAU
Laboratotre de Phystque Quantlque, Unttd Assoctde (505) du Centre Nattonal de la Recherche Sctenttftque, UmversttJ Paul Sabatwr, 118 route de Narbonne, 31062 Toulouse Cedex, France Received 3 Apral 1989, accepted for publication 6 June 1989 A non-empirical Helsenberg Harmltoman denved from the L12 or Na 2 ab ~mtlo potential curves, is applied to surface problems of the alkah metals The process consists in the fourth order perturbation of a N6el state taken as zeroth order wavefunctlon Besides the bcc bulk characteristics, wluch are correctly reproduced, the relaxations on the (100) and (110) surfaces seem to be correctly reproduced (contractions of about 35~ and < 1% amphtude respectively) The method enables one to study the adsorption of an atom on the surface, the site and the strength of the binding as well as the activation energy for magration