Conclusions
The initial configuration of Yttrium oxide clusters
(Y2O3)n(n=1-15) was
creatively constructed by combining artificial bee colony algorithm with
density functional theory. The structures of large and medium-sized
yttrium oxide clusters with molecular number greater than 10 were
established for the first time, and their ground state structures were
determined by structural optimization and frequency analysis in Gaussian
09 software package. The average binding energy, second-order difference
energy, H-L energy gap,density of states and thermodynamic properties of
each structure were calculated and analyzed in detail.the result shows:
- For small clusters with n<5, oxygen atoms and yttrium atoms
tend to form cage-like clusters. With the increase of size (n=6-15),
the clusters structure change from cage-like to space stair-like, and
gradually evolves into stable ellipsoid-like structure.
- The stability and molecular orbital of the clusters were analyzed in
detail, and it was found that the cluster structure was generally
stable. Because the valence bond orbital of oxygen atom is less than
half full (2P4), and the valence bond orbital of
yttrium atom is full (5S2), the probability of
electron filling p orbital is much larger than that of filling s
orbital, so the binary mixed yttrium oxide clusters have more stable
structures than the single yttrium clusters. When the number of
cluster molecules n=2,4,7,9, the relative stability is higher, and the
second-order energy difference score is basically consistent with the
results of H-L energy gap in determining the stability of cluster
structure. The major contribution from S basis function of oxygen
(magenta curve) is due to low-lying MOs instead of frontier MOs. HOMO
is almost purely contributed by yttrium orbitals.
- Cp, H and S of
(Y2O3)n increased with
the increase of T, and increased with the increase of cluster size.
Gv decreases with the increase of temperature, and the
change rule with cluster size is greatly affected by T. In the
temperature range of 300K-500K, the Gv lines intersect
each other, indicating that the stability of nanoclusters has changed
in the temperature range of 300K-500K. The thermodynamic properties of
(Y2O3)n vary greatly
with the number of clusters, which is similar to the size effect of
the thermodynamic properties of nanoscale materials.
The structure and related thermodynamic data of nanoclusters calculated
in this study have certain guiding significance for studying the
nucleation of yttrium oxide crystals from the perspective of
nanothermodynamics.