Premium
Phenakite‐Type BeP 2 N 4 —A Possible Precursor for a New Hard Spinel‐Type Material
Author(s) -
Pucher Florian J.,
Römer S. Rebecca,
Karau Friedrich W.,
Schnick Wolfgang
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201000153
Subject(s) - spinel , isostructural , type (biology) , bulk modulus , corundum , crystallography , phase transition , bar (unit) , enthalpy , chemistry , coordination number , crystal structure , thermodynamics , mineralogy , materials science , physics , metallurgy , geology , ion , paleontology , organic chemistry , meteorology
BeP 2 N 4 was synthesized in a multi‐anvil apparatus starting from Be 3 N 2 and P 3 N 5 at 5 GPa and 1500 °C. The compound crystallizes in the phenakite structure type (space group R $\bar 3$ , no. 148) with a =1269.45(2) pm, c =834.86(2) pm, V =1165.13(4)×10 6 pm³ and Z =18. As isostructural and isovalence‐electronic α‐Si 3 N 4 transforms into β‐Si 3 N 4 at high pressure and temperature, we studied the phase transition of BeP 2 N 4 into the spinel structure type by using density functional theory calculations. The predicted transition pressure of 24 GPa is within the reach of today’s state of the art high‐pressure experimental setups. Calculations of inverse spinel‐type BeP 2 N 4 revealed this polymorph to be always higher in enthalpy than either phenakite‐type or spinel‐type BeP 2 N 4 . The predicted bulk modulus of spinel‐type BeP 2 N 4 is in the range of corundum and γ‐Si 3 N 4 and about 40 GPa higher than that of phenakite‐type BeP 2 N 4 . This finding implies an increase in hardness in analogy to that occurring for the β‐ to γ‐Si 3 N 4 transition. In hypothetical spinel‐type BeP 2 N 4 the coordination number of phosphorus is increased from 4 to 6. So far only coordination numbers up to 5 have been experimentally realized (γ‐P 3 N 5 ), though a sixfold coordination for P has been predicted for hypothetic δ‐P 3 N 5 . We believe, our findings provide a strong incentive for further high‐pressure experiments in the quest for novel hard materials with yet unprecedented structural motives.