On the pressure-induced loss of crystallinity in orthophosphates of zinc and calcium
A recently suggested mechanism for the stress memory of various metal phosphates is investigated experimentally. Based on first-principles simulations [ N. J. Mosey , Science 307 , 1612 ( 2005 ) ], it had been argued that atoms with flexible coordination, such as zinc or heavy-metal cations, act as...
Gespeichert in:
Veröffentlicht in: | The Journal of chemical physics 2008-02, Vol.128 (7), p.074706-074706-10 |
---|---|
Hauptverfasser: | , , , , , , , |
Format: | Artikel |
Sprache: | eng |
Online-Zugang: | Volltext |
Tags: |
Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
|
Zusammenfassung: | A recently suggested mechanism for the stress memory of various metal phosphates is investigated experimentally. Based on first-principles simulations [
N. J. Mosey
,
Science
307
,
1612
(
2005
)
], it had been argued that atoms with flexible coordination, such as zinc or heavy-metal cations, act as network-forming agents, undergoing irreversible pressure-induced changes in bonding that lead to increased connectivity between phosphate anions. In the present study, orthophosphates of zinc and calcium were exposed to high pressures on surfaces and in diamond anvil cells. An additional set of first-principles simulations was accomplished on
α
-orthophosphate of zinc, which suggested that this material was already cross-linked before compression but that it nevertheless underwent a reversible coordination change under pressure in agreement with the experimental results presented here. Raman spectra indicate an irreversible, pressure-induced loss of long-range crystallinity. The pressures required to induce these changes are around
7
GPa
for the zinc phosphates, while they are close to
21
GPa
for the calcium phosphates. Hydrogenation of the metal phosphate lowers the threshold pressure by approximately
2
-
3
GPa
in both cases. Moreover,
α
-orthophosphate of zinc could be partially amorphisized under nonisotropic pressure on copper foils. |
---|---|
ISSN: | 0021-9606 1089-7690 |
DOI: | 10.1063/1.2837809 |