Article
Structure, elasticity, thermodynamics and high pressure behavior of ZnB 4O 7 and CdB 4O 7
Fecha
2012Registro en:
10.1016/j.solidstatesciences.2012.05.008
Autor
Winkler, B.
Castellanos Guzman, A.G.
Wiehl, L.
Bayarjargal, L.
Milman, V.
Institución
Resumen
An accurate single crystal determination of the structure of ?-ZnB 4O 7 is reported, and an improved description of the polyhedral network is presented. The experimental data are used to evaluate density functional theory calculations. Structural models based on the PBESOL exchange-correlation functional were in slightly better agreement with experimental data than those employing the PBE exchange-correlation functional. However, in both cases the agreement between the results of the experiments and the calculations was very satisfactory. The models were therefore used to predict the compression behavior (B?-ZnB 4 O7=59.9(7) GPa), the elasticity tensor, bond populations, and a transition pressure of 3.7 GPa for the transition into the high pressure ?-phase. The predicted bulk modulus of the high pressure polymorph is B?-ZnB 4 O7=210.4(4) GPa. The heat capacity of the ?-phase has been determined with quasi-adiabatic microcalorimetric measurements and at low temperatures a Debye temperature of ? = 787 K has been obtained. The results obtained for ?- and ?-ZnB 4O 7 are compared to those of the isostructural CdB 4O 7 compounds. The transition from the ?- to a high pressure ?-phase of CdB 4O 7 is predicted to occur at ?1.9 GPa, but within the uncertainty of the model, the high pressure phase may also be isostructural to ?-CaB 4O 7. 2012 Elsevier Masson SAS. All rights reserved.