FIGURE 3 Optimized structures of
OM3@(GY/GDY/GTY) (M = Li, Na, and K)
unit of OM3@GY (M = Li, Na, and K) exhibits a slight
corrugation, especially for ONa3@GY. In contrast, the
OM3 units in OM3@GDY (M = Li, Na, and K)
are all above the central position of the pore and the three alkali
atoms point to three benzene rings, respectively. It is clearly seen
that the structural features of
(ONa3/OK3)@GTY are similar to those of
OM3@GDY. Interestingly, unlike other structures,
small-sized OLi3 is embedded inside the large pore of
GTY, which leads to a planar structure of OLi3@GDY, as
shown in red box in Figure 3. Except for OLi3 in
OLi3@GTY, all the other OM3 units
distort from a triangle to an umbrella shape. Table 1 shows that average
O–M bonds of the OM3 unit in
OM3@(GY/GDY/GTY) are slightly elongated compared with
the corresponding O–Li (1.683), O–Na (2.053), and O–K (2.404 Å) bonds
in isolated OM3. This indicates that the interaction
between OM3 and GYs has little impact on the M–O
chemical bonds. The vertical distance (d ) between
OM3 and the graphyne surface (GY, GDY, and GTY) is also
given in the table, which exhibits an increasing trend with increasing
atomic number of M.
TABLE 1 The average O–M bond lengthsR O–M (Å), vertical distances between the O atom
and plane d (Å), interaction energies E int(kcal mol-1), MK charges on the OM3units q (|e |), and vertical ionization
potentials VIP (eV) of the OM3@GYs (M = Li, Na, and K)