Extended coupled-cluster applicability

If affordable, there is a range of very accurate coupled-cluster and symmetry-adapted perturbation theories available which can approach spectroscopic accuracy [57, 200, 201]. However, these are only applicable to the smallest alcohol cluster systems using currently available computational resources. Near-linear scaling algorithms [192] and explicit correlation methods [57] promise to extend the applicability range considerably. Furthermore, benchmark results for small systems can guide both experimentalists and theoreticians in the characterization of larger molecular assemblies. 

Computationally, the present approach rests on the QVC coupling scheme in conjunction with coupled-cluster electronic structure calculations for the vibronic Hamiltonian, and on the MCDTH wave packet propagation method for the nuclear dynamics. In combination, these are powerful tools for studying such systems with 10-20 nuclear degrees of freedom. (This holds especially in view of so-called multilayer MCTDH implementations which further enhance the computational efficiency [130,131].) If the LVC or QVC schemes are not applicable, related variants of constructing diabatic electronic states are available [132,133], which may extend the realm of application from the present spectroscopic and photophysical also to photochemical problems. Their feasibility and further applications remain to be investigated in future work. 

Nevertheless, some effort has been extended toward developing coupled-cluster treatments that are either exactly or partially spin-adapted. Rigorously spin-adapted methods have been presented in the literature [214-216], but most applications have used either the partially spin-adapted variants [217,218] and the spin-restricted approach [219] in which the expectation value of (S2) is... 

The coupled-cluster method (CC) is another very promising procedure for constructing correlated wave functions in a systematic way.43 Unlike Cl, CC can be used also for extended systems.44 A remarkable example of its efficiency is provided by applications to the electron gas for both high,... 

The method described in this section was first proposed by W. Klopper [99] and first applied in the context of finite perturbation theory. It was later extended by Franke and van Wullen [101]. For a recent application combined with MC-SCF and approximate MC-SCF-based coupled-cluster methods see Ref. [100]. 

A particular variant of the coupled cluster method, called Fock-space or valence-universal [49,50], gave remarkable agreement with experiment for many transition energies of heavy atoms [51]. This success makes the scheme a useful tool for reliable prediction of the structure and spectrum of superheavy elements, which are difficult to access experimentally. A brief description of the method is given below. A more flexible scheme with higher accuracy and extended applicability, the intermediate Hamiltonian Fock-space coupled cluster approach, is shown in the next section. 

The purpose of this work is to extend Sekino and Bartlett s approach - which we will refer to as a linearized EOM coupled cluster (EOM-CCl) method - to computations of the frequency-dependent optical rotations of chiral molecules. The development of coupled cluster methods in this field has been dedicated to the implementation of streamlined models of chiroptical properties that are applicable to large molecules[27,28], and this work represents apossible step toward that goal. We will compare the performance of the EOM-CCl approach to its linear-response counterpart - both in terms of theoretical predictions and computational efficiency - for the rigid chiral molecules (5 )-methyloxirane, (5)-2-chloropropionitrile, and (1S,4S)-norbornenone, as well as the conformationally flexible species (/ )-epichlorohydrin. 

The coupled-cluster model represents a significant improvement on the truncated Cl model in that it provides a description of the electronic structure that is both size-extensive and noore compact. On the other hand, it has proved difficult to extend the application of coupled-cluster theory to... 

The coupling of encapsulation technologies with cell culture techniques permits the extended use of these bioreactors with complex tissue systems such as islet clusters. Existing reactor systems are also useful in obtaining the basic transport and reaction kinetics parameters necessary to design the novel devices required for biomedical applications. In summary, the relevance of this work to the biotechnology and health care-based industries is in the development, of artificial organ systems, extra-corporeal devices to... 

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