4. 参考文献要近些年或早期经典，并且水平要高，中心期刊以上。
举例如下：
(1) Alumina and chromia are very important materials in the surface coatings industry, e.g.
for corrosion protection, catalyst supports, dielectric insulators, etc. The type of defects and the
associated formation energy in these materials are of great importance for atomic transport and
mechanical properties, and are of direct relevance to the surface stability and reaction kinetics.
Within the constraints of charge neutrality and stoichiometry, only two types of native point
defects are allowed in α-A12O3 and α-Cr2O3, i.e. Schottky and Frenkel defects. There are
numerous theoretical studies on these intrinsic point defects in the corundum-type crystals, e.g.
A12O3 (Refs. [1–4]), Cr2O3 (Refs. [4–6]) and Fe2O3 (Refs. [4,5,7]). Most of these studies
employed the same empirical shell model [8] (albeit with different parameter sets) combined with
the Mott–Littleton approximation [9], although Catlow et al. [2,5] and Lawrence [6] also carried
out calculations with an interatomic potential from a modified form of the electron-gas
approximation. Very recently, first-principles calculations have been performed for intrinsic
defects in α-A12O3 [10]. However, there is still some controversy over the dominant defect type
in α -A12O3. Some calculations [2,3] indicate that oxygen Frenkel defects have a lower
formation energy than Schottky defects, while others [1,2,4,10] come to the opposite conclusion.
As pointed out by Catlow et al. [2], this may in part be due to the difference in potential
parameters used for describing the properties of α -A12O3. As mentioned above, to date the
Mott–Littleton approximation has been the predominant method to carry out calculations of
defect energies. In contrast to first-principles calculations, the main advantages of the Mott–
Littleton method are its easy implementation and low computational cost. In general, it is thought
that approximately 100 atoms around a defect are sufficient for a convergence of the Mott–
Littleton calculations [2]. However, about 40 atoms or less were also used to calculate defect
energies [1,4]. Hence, it is necessary to examine the convergence of the results when the Mott–
Littleton method is used. In a previous paper [11] we developed a very simple potential from the
model put forward by Matsui [12], which can describe the structure and lattice energy of α
-A12O3 very well. This “modified” Matsui model is very similar to shell models, except that in
the latter a point charge is separated into a shell and a core. The shell is attached to the core by a
spring and the overlap of shells results in a short-range repulsion. This modification leads to
several additional parameters in the interaction potential, which requires at least the same number
of experimental observables for their parameterisation [13]. In the present paper we will transfer
this modified Matsui potential from α-A12O3 to α-Cr2O3 in order to calculate the native point
defect energies for both crystals. The convergence of the calculations using the Mott–Littleton
approximation will be tested, the predicted order of native defect energies in stoichiometric α
评论0