Transcript Diapositive 1

La2MgNi2H8, the first
mixed polyanionic
transition metal hydride
J-N. Chotard, Y. Filinchuk, K. Yvon
SSCr Meeting, Bern, 2006
J-N. Chotard, Y. Filinchuk, K. Yvon
Introduction
Complex metal hydrides
~ 80 compounds containing ~ 30 different
transition metal hydride complexes:
almost all of them are mononuclear
1st polynuclear hydride complexes based on 3d-metal
[Ni2H7]7- & [Ni4H12]12-
SSCr Meeting, Bern, 2006
J-N. Chotard, Y. Filinchuk, K. Yvon
Synthesis and structure determ.
•
La2MgNi2: arc-melting La
and Ni, sintering the
product with Mg
•
La2MgNi2H8:
hydrogenation/deuteration
in an autoclave:
30 bar, 100°C
High-resolution synchrotron powder diffraction (SNBL at ESRF):
indexing, metal structure (FOX), Rietveld
High-resolution neutron powder diffraction (HRPT, SINQ, PSI):
16 deuterium atom positions (FOX), Rietveld
SSCr Meeting, Bern, 2006
J-N. Chotard, Y. Filinchuk, K. Yvon
Structure of La2MgNi2H8
Metal atom shifts < 0.65 Å
La2MgNi2
La2MgNi2H8
Tetragonal
Monoclinic
7.64
3.94 Å
SSCr Meeting, Bern, 2006
11.84
7.82
11.96 Å
92.78 °
J-N. Chotard, Y. Filinchuk, K. Yvon
Two types of D-atom positions
La2MgNi2
La2MgNi2H8
SSCr Meeting, Bern, 2006
J-N. Chotard, Y. Filinchuk, K. Yvon
Bonding :18 electron rule
La3+, Mg2+
34 electrons
[Ni2H7]7-, [Ni4H12]12-, H64 electrons
This concept is supported by observed changes in physical properties
SSCr Meeting, Bern, 2006
J-N. Chotard, Y. Filinchuk, K. Yvon