Density Functional Theory
Density Functional Theory
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DOI：
10.1007/978-3-662-09638-3_1
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
N. Handy
中科院分区：
文献类型：
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作者：
N. Handy
量子化学的主题可能已经陷入了僵局。保持从头计算量子化学的讨论，我们现在知道如何做非常大的SCF计算，这要归功于Almlof [lj]直接方法的引入。我们也可以设法用好的基组来进行这样的计算，尽管我认为6- 3 IG * 还不够好，而且可能需要更接近TZ 2 P的基组来进行确定的SCF计算。除了SCF之外，还有一些主要的困难，都与试图更准确地表示电子-电子尖点有关。我们从Kutzelnigg [2]的工作中知道，这个问题的收敛非常慢，类似于（I+ lt 4;这意味着相关计算需要非常大的基组。我们知道，它是更重要的是包括d和f基函数比改进的方法。6- 3 IG * 碱基不适用于相关研究。我们还知道，相关方法MP2，MP3，MP4，CISD，CCSD，CCSD（T）的原始成本随着问题大小的幂5，6，7，6，6，7而增加。用1000个基函数进行CCSD（T）计算是根本不可能的，在本世纪也不可能进行这样的计算。我认为，我们已经被误导的快速进展，计算机公司已经取得了发展，他们的硬件：更多的内存，矢量化编译器，并行机，所有这些我们已经利用，但这些进步将不会治愈我们的突出的基础上设置的问题。
The subject of quantum chemistry may have reached an impasse. Keeping the discussion to ab initio quantum chemistry we now know how to do very large SCF calculations, thanks to the introduction of the Direct methodology by Almlof [lj. We can also manage to work with good basis sets for such calculations, although I consider that 6-3IG* are not good enough, and probably something nearer to TZ2P is required for definitive SCF calculations.Beyond SCF there are major difficulties, all associated with trying to more accurately represent the electron-electron cusp. We know from the work of Kutzelnigg [2j that the convergence of this problem is very slow, something like (I+ lt4; this means that very large basis sets are required for correlated calculations. We know that it is more important to include d and f basis functions than to improve the methodology. 6-3IG* bases are not appropriate for correlated studies. We also know that the raw cost of correlated methods, MP2, MP3, MP4, CISD, CCSD, CCSD (T) increase with powers of the size of the problem as 5, 6, 7, 6, 6, 7. It is simply not possible to contemplate CCSD (T) calculations with 1000 basis functions, nor will it be sensibly possible to contemplate such calculations this century. I suggest that we have been misled by the rapid progress that computer companies have made in the development of their hardware: more memory, vectorisation compilers, parallel machines, all of which we have taken advantage of, but these advances will not cure our outstanding basis set problems.