Structural ordering in Cd(x)Pb(1-x)F2 alloys: a combined molecular dynamics and solid state NMR study.
Molecular dynamics (MD) simulations of binary Cd(x)Pb(1-x)F(2) alloys have been carried out, using a two-body Buckingham interaction potential, leading to a correct description of structural properties as a function of composition and pointing towards an understanding of the eutectic phenomenon. The simulation data can be analyzed in terms of five local fluorine environments Q((n)) (4> or =n> or =0), where n is the number of Pb nearest-neighbor environments. The results suggest a highly nonstatistical population distribution, suggesting an intrinsic phase segregation tendency in the undercooled melt, during the cooling process. This prediction has been tested experimentally for six representative compositions (0.2< or =x< or =0.7) on the basis of high-resolution (19)F solid state NMR data, revealing important similarities between theory and experiment. While the NMR data confirm that the population distribution is, indeed, nonstatistical for all compositions, the results are only found to be consistent with an intrinsic segregation tendency of PbF(2)-rich domains. This tendency manifests itself in substatistical populations of Q((3)) units, resulting in preferred Q((2)) and Q((4)) formations.
Instituto de Fisica de São Carlos, USP, C.P. 369, 13560-970 São Carlos, São Paul, Brazil.
Adalberto
A
Picinin
Rashmi R
RR
Deshpande
Andrea S S
AS
de Camargo
José Pedro
JP
Donoso
José Pedro
JP
Rino
Hellmut
H
Eckert
Maurício A P
MA
Silva