#（参考了知乎LDA+U讲解）
------------------------------------------------------------以下是本帖子原文-------------------------------------------------------------------
CeO2的块体结构优化，按照文献描述写了输入文件，优化结果晶格参数a=5.40 vs 文献上的 a=5.485，想完全重复文献，没重复出来。想请高手看看哪里出了问题：
文献方法如下：
2. THEORETICAL METHODS AND COMPUTATIONAL
DETAILS
Spin-polarized DFT and supercell periodic models were used within the Vienna ab initio simulation package (VASP, version5.2.12).24−26 We treated explicitly the C (2s, 2p), O (2s, 2p), Ni (3p, 3d, 4s), and Ce (4f, 5s, 5p, 5d, 6s) electrons as valence states expanded in plane-waves with a cutoff energy of 415 eV, whereas the remaining electrons were kept frozen as core states in the projector-augmented wave (PAW) method.27
Total energies and electron densities were computed within the DFT+U approach of Dudarev et al.,28 in which a Hubbard U-like term (Ueff = U − J, that is, the difference between the Coulomb U and exchange J parameters, hereinafter referred to as simply U) is added to the Perdew−Burke−Ernzerhof (PBE) generalized-gradient approximation (GGA) functional.29 We used a value of U = 4.5 eV for Ce atoms, which was calculated self-consistently by Fabris et al.30 using a linear response approach.31
The O-terminated CeO2(111) and Ni(111) surfaces were modeled by (3 × 3) unit cells, containing six atomic layers
separated by at least 18 Å of vacuum. Monkhorst-Pack grids with 2 × 2 × 1 and 4 × 4 × 1 k-point sampling were used for
the CeO2(111) and Ni(111) surfaces, respectively. All of theatoms in the three bottom layers were fixed at their optimized
bulk-truncated (aCeO2 = 5.485 Å; aNi = 3.518 Å) positions during geometry optimization, whereas the rest of atoms were
allowed to fully relax. All of the reaction energies (Ereac) were referenced to C, CO, or CO2 as a gas-phase species for which
Γ-point calculations were performed in at least 12 × 12 × 12 Å3 boxes. A similar computational setup was used for the
calculation of pure gas-phase Ni1, pyramidal Ni4, and rhombohedral Ni4 clusters
我的输入文件如下：
(, 下载次数 Times of downloads: 0)
上传 Uploaded
点击下载Click to download
(, 下载次数 Times of downloads: 2)
上传 Uploaded
点击下载Click to download
POTCAR：PAW_PBE O 08Apr2002 PAW_PBE Ce 23Dec2003
KPOINTS：
Auto
0
Gamma
4 4 4
0.0 0.0 0.0
