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Alistair P. Rendell Martyn F. Guest Rick A. Kendall 《Journal of computational chemistry》1993,14(12):1429-1439
The recently developed parallel coupled-cluster algorithm of Rendell, Lee, and Lindh [Chem. Phys. Lett., 194 , 84 (1992)] is extended to allow four-indexed quantities containing one or two indices in the virtual orbital space to be stored across the global memory of distributed-memory parallel processors. Quantities such as the double-excitation amplitudes can now be distributed over multiple nodes, with blocks of data retrieved from remote nodes by the use of interrupt handlers. As an application of the new code, we have investigated the potential energy surface of the 2-hydroxypyridine/2-pyridone tautomers. Using large basis sets, the structure of each tautomer and the transition state connecting the two minima has been determined at the SCF level. The relative energy difference and the activation energy were then redetermined using the MP2, CCSD, and CCSD(T) methods. All calculations have been performed on Intel distributed-memory supercomputers. The largest coupled-cluster calculations contained over 2 million double-excitation amplitudes. © John Wiley & Sons, Inc. 相似文献
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Laser cooling and magnetic trapping of (85)Rb atoms have been performed in extremely strong and tunable magnetic fields, extending these techniques to a new regime and setting the stage for a variety of cold atom and plasma experiments. Using a superconducting Ioffe-Pritchard trap and an optical molasses, 2.4 x 10(7) atoms were laser cooled to the Doppler limit and magnetically trapped at bias fields up to 2.9 T. At magnetic fields up to 6 T, 3 x 10(6) cold atoms were laser cooled in a pulsed loading scheme. These bias fields are well beyond an order of magnitude larger than those in previous experiments. Loading rates, molasses lifetimes, magnetic-trapping times, and temperatures were measured using photoionization and electron detection. 相似文献
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It is demonstrated, using the ground state of the water molecule, that the contribution of triply excited configurations to electron correlation energies in closed-shell systems is more sensitive to the degree of completeness of the basis set than the component associated with quadruply excited configurations. The relative importance of the triply excited states increases more rapidly than that of the quadruple excitations, as the quality of the basis set is improved. 相似文献
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Lydia A. Panther Dr. Daniel P. Guest Dr. Andrew McGown Hugo Emerit Dr. Raysa Khan Tareque Dr. Arathy Jose Mr. Chris M. Dadswell Dr. Simon J. Coles Dr. Graham J. Tizzard Dr. Ramón González-Méndez Dr. Charles A. I. Goodall Prof. Mark C. Bagley Prof. John Spencer Dr. Barnaby W. Greenland 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(49):e202201444
Solvent-free synthesis by using a vibratory ball mill (VBM) offers the chance to access new chemical reactivity, whilst reducing solvent waste and minimising reaction times. Herein, we report the core functionalisation of N,N’-bis(2-ethylhexyl)-2,6-dibromo-1,4,5,8-naphthalenetetracarboxylic acid (Br2-NDI) by using Suzuki, Sonogashira and Buchwald–Hartwig coupling reactions. The products of these reactions are important building blocks in many areas of organic electronics including organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic photovoltaic cells (OPVCs). The reactions proceed in as little as 1 h, use commercially available palladium sources (frequently Pd(OAc)2) and are tolerant to air and atmospheric moisture. Furthermore, the real-world potential of this green VBM protocol is demonstrated by the double Suzuki coupling of a monobromo(NDI) residue to a bis(thiophene) pinacol ester. The resulting dimeric NDI species has been demonstrated to behave as an electron acceptor in functioning OPVCs. 相似文献