Bond lengths and dissociation energy of
The optimized exhibits a square
planar D4h symmetry with Au ions in the center connected
to the four Xe atoms and has a 2B1gelectronic ground state.Table 2 shows that our theoretically determined
equilibrium distance for at the MP2
level is 2.711 Å, which is slightly lower than the experimental value.
By contrast, the corresponding B3lyp value
is 2.85 Å, which is higher by
approximately 0.1 Å compared with the experimental value. We note that
the MP2 and B3lyp results for by Seidel(24) using
pseudopotentials and small basis sets are 2.871 and 2.787
Å, respectively. Seidel predicted
that the bond distances at the B3lyp and MP2 levels are longer than our
results by as much as 0.02 and 0.07 Å, respectively, thereby
demonstrating the need for large
basis sets to describe these weak
interaction systems. Li (55) reported that the
calculated value (2.714 Å) at the high theoretical level ccsd(T) is
nearly identical to the experimental ones. Thus, a
high theoretical level ccsd(T) with
a large basis set will produce results close to the experimental value
limit. However, theoretical level
MP2 is an optimal compromise choice between accuracy and cost for our
full calculations on weak interaction systems considering computational
feasibility. Our result at the MP2 level is reliable.
We now discuss the dissociation energy of . Table 3 shows that is
predicted to be stable toward dissociating into
Au2+ and 4Xe at
all levels of theory employed in our
study. The predicted dissociation
energy Do corrected by the BSSE and ZPE varies between 189.136 and
238.583 kcal/mol (Table 3). The
mean dissociation energy with respect to Au2+ and 4Xe
is predicted to be approximately 208 kcal/mol (taking the average of the
last two columns in Table 3). This value is a little higher than the 200
kcal/mol mean dissociation energy predicted
by Seidel(24). The
predicted bond distance (2.891 Å) at the HF level by Seidel is very
long. Hence, the 144 kcal/mol dissociation energy calculated at the HF
level by Seidel is unreliable and underestimates the mean dissociation
energy with respect to Au2+ and 4Xe. Thus, the mean
dissociation energy (208 kcal/mol) is reasonable with respect to
Au2+ and 4Xe.
Existence
and stability prediction ofbased on Born–Haber
cycles
A synthetic route according to
reaction 1 could be adopted to prepare the salt compound. Figure 1 shows
the corresponding Born–Haber cycle.