42 lines
2.7 KiB
XML
42 lines
2.7 KiB
XML
== Atomic model establishment
|
||
|
||
我们建立了三类模型：无缺陷、点缺陷和面缺陷。
|
||
|
||
Three types of models were established: defect-free models, point defect models, and surface defect models.
|
||
|
||
无缺陷和点缺陷的模型
|
||
|
||
无缺陷和点缺陷的模型尺寸约为 $12.4 angstrom times 10.7 #sym.angstrom times 10.1 #sym.angstrom$，包含了大约 128 个原子。
|
||
我们认为是足够大的，因为无缺陷模型的结果与实验差距在一定范围内，且继续扩大模型对准确程度没有提升。
|
||
对于点缺陷模型，我们考虑了 Si 空位、C 空位、N 替位、Al 替位。
|
||
分别记为 V#sub[Si]、V#sub[C]、N#sub[Si] 和 Al#sub[C]。
|
||
考虑到 SiC 的对称性 p63mc （引用），有两个不同的位点，记为 k 和 h，
|
||
根据局部环境近似为立方（k）还是六角（h）。
|
||
此外，还有人提出，N 替换 C、C 替换 Si 的模型（引用），
|
||
此结构除了 h 位与 k 位的区别以外，还需要考虑发生替换的两个原子位于面内还是面外（将会导致对称性的不同）。
|
||
|
||
The defect-free and point defect models were established using supercells
|
||
with dimensions of $12.4 #sym.angstrom times 10.7 #sym.angstrom times 10.1 #sym.angstrom$,
|
||
containing approximately 128 atoms.
|
||
This supercell size was found sufficient for accurately capturing the phonon properties
|
||
of both defect-free and point-defect-containing 4H-SiC,
|
||
as the calculated phonon frequencies for the defect-free model deviated by less than 5% from experimental values,
|
||
and further enlargement of the supercell yielded negligible changes.
|
||
Twelve point defect models were constructed,
|
||
including Si vacancies (V#sub[Si]-h and V#sub[Si]-k), C vacancies (V#sub[C]-h and V#sub[C]-k),
|
||
N substitutions at C sites (N#sub[C]-h and N#sub[C]-k),
|
||
Al substitutions at Si sites (Al#sub[Si]-h and Al#sub[Si]-k),
|
||
and complex defects involving N substitution at a C site followed by C substitution at a Si site
|
||
@gerstmann_formation_2003
|
||
(N#sub[C]C#sub[Si]-i-h, N#sub[C]C#sub[Si]-i-k, N#sub[C]C#sub[Si]-o-h and N#sub[C]C#sub[Si]-o-k).
|
||
Here, the suffixes -h and -k denote the quasi-hexagonal and quasi-cubic sites, respectively,
|
||
while -i and -o denote the in-plane and out-of-plane configurations.
|
||
|
||
（图：a hk 位置 b 复杂缺陷 强调在复杂缺陷中，h k 根据 N 原子而定）
|
||
|
||
面缺陷的模型
|
||
|
||
对于面缺陷模型，主要考虑了三类 BPD（引用自己的文章），这些缺陷在室温下被认为是可以稳定存在的。
|
||
对于每类BPD，我们考虑两个模型，一个将两个 PD 包括在内，为了模拟 PBD 未分解或分解后边缘处的信号；
|
||
另一类则仅仅包含一个贯穿的层错，为了模拟 BPD 分解后在层错处的信号。
|