Doping clusters

Structural stability of 26 models were investigated for X-doped clusters of X B6, X B12-co, and X B12-ico based on each of the optimized supercells with nondoped clusters, namely B6, Bi2-co, and B12-ico. We introduced the atom X (X=H-Br) into the center of the optimized nondoped cluster, and optimized the atomic structure again, then we estimated the formation energy (Ef) of the X-doped clusters defined as ... 

Figure 4. FT-ICR mass spectra showing evidence for the production of boron and boron/potassium doped 60-ati n fuiloenes. The bottom panel shows the result of reaction with ammonia. Note that the boron-doped clusters have been titrated with ammonia, demonstrating that the boron is substituting for a carbon as part of the fullerene cage. Note also that the clusters in the top panel marked K(K C4o) and K2(K C o) are missing after reaction with ammonia in the bottom panel, demonstrating that the extra potassium atoms were on the outside, unprotected by the fullerene cage.

Multiconfiguration molecular orbital calculations are performed on clusters with two copper atoms, (Cu20n) and (Cu20n) , embedded in a crystal environment for La2-xBaxCu04 (a crystal environment for Fa2-xSrxCu04 is essentially the same), where the former corresponds to the parent undoped cluster and the latter to the one-hole doped cluster. ... 

Finally, we stress that the quantum chemical method presented here has the advantage over DFT-based techniques that it also furnishes wavefunctions that can be used to perform computations of spectra, and therefore have a better contact with the experiment. Another advantage of this approach is that, unlike the diffusion Monte-Carlo method, it can coherently be applied to studies of fermion and mixed boson/fermion doped clusters. An example can be found in our recent work on the Raman spectra of (He)w-Br2(X) clusters [27,28]. 

Superconductivity. The insulator-superconductor transition takes place near this composition probably as a result of the percolation of the hole doped clusters. At x = 6.342 small amounts of the material become superconducting (fig. 27b). Superconductivity under pressure A giant ATJAP effect has been measured at RT (sect. 5.4) indicating an increased compressibility at the T-0 transition due to the half-filled chains and strong oxygen-ordering effects. The effect disappears at LT where the mobility of oxygen freezes (fig. 58). 

One of the first applications of RQMC was to the rotational dynamics of carbonyl sulfide (OCS) molecules solvated in helium clusters, for cluster sizes (tV = 3,10) [42]. This and related work, described shortly, rest on the absorption spectrum given by the Fourier transform of the reptilian imaginary time electric dipole correlation function. Similarly, the optical activity is extracted from the autocorrelation of the molecular orientation vector. This work by Moroni and coworkers and/or Boroini and co-workers was closely followed by several other investigations of rotational dynamics in doped clusters, summarized as follows ... 

Returning now to CO doped clusters, the RQMC method was used to calculate... 

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