Abstract
We present a theoretical approach to investigate the possibility of reducing desorption temperature of
Li
N
H
2
by partial element substitution. The approach was based on a first-principles study of electronic structure of
Li
N
H
2
and
(
Li
,
Mg
)
N
H
2
. Results of the
Li
N
H
2
study showed that
Li
N
H
2
is nonmetallic, the bonding between Li and N is ionic, and the bonding between N and H is strongly covalent. Results of the
(
Li
,
Mg
)
N
H
2
study showed that the bonding nature of Li-N and N-H is the same as in
Li
N
H
2
, but the bond strength of N-H was reduced. In addition, the system becomes metal-like after substitution. These two major differences can be used to explain the experimental observation that the hydrogen desorption temperature was reduced by Mg substitution. More important, they might be used as criteria to predict the behavior of other substitution elements.