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你可以看下VASP的Tutorial的OUTCAR小节，里面留了个问题：
The reference system for which the pseudopotentials have been generated are isolated, nonspinpolarized atoms. Why is the total energy (energy without entropy) in this calculation close to zero?
然后你点一下那个click to see answer，有如下内容：
In this calculation, the total energy (energy without entropy) of the single, isolated oxygen atom is close to zero. And actually, if the box size were larger and the precision of the calculation higher, it would go to zero. This is only because all pseudopotentials have been generated for isolated, nonspinpolarized atoms. So we are comparing the reference system with itself. Keep in mind that, while the choice of the reference system is generally arbitrary, as soon as you do calculations for more atoms or in a smaller box, i.e., not isolated systems, the absolute values of energies become physically meaningless. In general, only relative energies (band energies w.r.t. Fermi level, total energies of two related systems etc.) can be interpreted and have physical meaning.
这里需要补充的是，你要注意实际上这里扣除的是各个原子的参考能量之和，这个参考能量是原子在赝势/PAW生成阶段按照孤立情况下非自旋极化处理的，因此这个能量不完全能和结合能对应。
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发表于 Post on 2024-9-18 10:47:57
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