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Acetylene clusters are prototypical of simple non-aromatic systems bonded through C–H…π interactions. The present work explores structures and properties of acetylene clusters (C2H2) n , n = 8 and 10, employing cluster-building algorithm and molecular tailoring approach (MTA). The former uses electrostatics guidelines for building (C2H2)8 and (C2H2)10 structures. These clusters are treated at MP2 level of theory with correlation-consistent basis sets using MTA. The Hessian matrix and vibrational spectra for the best five structures of (C2H2)8 and (C2H2)10 are computed employing MTA. Actual calculations on these clusters using conventional methods employing large basis sets are prohibitively difficult to perform. All the frequencies for these structures extracted using MTA-based Hessian matrix are found to be real, confirming their local minimum nature. This study points to the possibility of using the present approach for exploring structures, energetics and vibrational spectra of even larger clusters at higher levels of theory.  相似文献
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Due to high scaling order of MP2 and CCSD(T) methods, it is either difficult or at times even impossible to treat even moderately sized molecular systems with elaborate basis sets such as aug-cc-pVXZ (X?=?D, T, Q). In the present work, several structures of acetylene pentamers and hexamers are explored at MP2 and CCSD(T) levels of theory as?prototypical examples of clusters bound by CH···?? interactions. To enable this investigation, fragment-based method Molecular Tailoring Approach (MTA) is employed. It is shown that these acetylene assemblies can be treated with substantial reduction in computational resources and time, yet retaining a sub-millihartree accuracy in the energy. Further, using standard extrapolation methodologies, stabilization energies at the complete basis set limit of the acetylene clusters under consideration are determined at MP2 and CCSD(T) levels of theory. To test out the feasibility of treating a large cluster at MP2 level, a demonstrative calculation on a dodecamer of acetylene is reported.  相似文献
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