Spin-adapted open-shell random phase approximation and time-dependent density functional theory. I. Theory
Li, Zhendong; Liu, Wenjian1
AbstractThe spin-adaptation of single-reference quantum chemical methods for excited states of open-shell systems has been nontrivial. The primary reason is that the configuration space, generated by a truncated rank of excitations from only one component of a reference multiplet, is spin-incomplete. Those "missing" configurations are of higher ranks and can, in principle, be recaptured by a particular class of excitation operators. However, the resulting formalisms are then quite involved and there are situations [e.g., time-dependent density functional theory (TD-DFT) under the adiabatic approximation] that prevent one from doing so. To solve this issue, we propose here a tensor-coupling scheme that invokes all the components of a reference multiplet (i.e., a tensor reference) rather than increases the excitation ranks. A minimal spin-adapted n-tuply excited configuration space can readily be constructed by tensor products between the n-tuple tensor excitation operators and the chosen tensor reference. Further combined with the tensor equation-of-motion formalism, very compact expressions for excitation energies can be obtained. As a first application of this general idea, a spin-adapted open-shell random phase approximation is first developed. The so-called "translation rule" is then adopted to formulate a spin-adapted, restricted open-shell Kohn-Sham (ROKS)-based TD-DFT (ROKS-TD-DFT). Here, a particular symmetry structure has to be imposed on the exchange-correlation kernel. While the standard ROKS-TD-DFT can access only excited states due to singlet-coupled single excitations, i.e., only some of the singly excited states of the same spin (S(i)) as the reference, the new scheme can capture all the excited states of spin S(i)-1, S(i), or S(i)+1 due to both singlet- and triplet-coupled single excitations. The actual implementation and computation are very much like the (spin-contaminated) unrestricted Kohn-Sham-based TD-DFT. It is also shown that spin-contaminated spin-flip configuration interaction approaches can easily be spin-adapted via the tensor-coupling scheme. (C) 2010 American Institute of Physics. [doi:10.1063/1.3463799]
KeywordConfiguration Interactions Density Functional Theory Excited States Mathematical Operators Rpa Calculations Tensors
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WOS IDWOS:000280941800009
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Cited Times:42[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Corresponding AuthorLiu, Wenjian
Affiliation1.Peking Univ, State Key Lab Rare Earth Mat Chem & Applicat, Inst Theoret & Computat Chem, Beijing Natl Lab Mol Sci,Coll Chem & Mol Engn, Beijing 100871, Peoples R China
2.Peking Univ, Ctr Computat Sci & Engn, Beijing 100871, Peoples R China
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GB/T 7714
Li, Zhendong,Liu, Wenjian. Spin-adapted open-shell random phase approximation and time-dependent density functional theory. I. Theory[J]. JOURNAL OF CHEMICAL PHYSICS,2010,133(6).
APA Li, Zhendong,&Liu, Wenjian.(2010).Spin-adapted open-shell random phase approximation and time-dependent density functional theory. I. Theory.JOURNAL OF CHEMICAL PHYSICS,133(6).
MLA Li, Zhendong,et al."Spin-adapted open-shell random phase approximation and time-dependent density functional theory. I. Theory".JOURNAL OF CHEMICAL PHYSICS 133.6(2010).
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