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141.
Thermal conductivities of molecular liquids by reverse nonequilibrium molecular dynamics 总被引:1,自引:0,他引:1
Zhang M Lussetti E de Souza LE Müller-Plathe F 《The journal of physical chemistry. B》2005,109(31):15060-15067
The reverse nonequilibrium molecular dynamics method for thermal conductivities is adapted to the investigation of molecular fluids. The method generates a heat flux through the system by suitably exchanging velocities of particles located in different regions. From the resulting temperature gradient, the thermal conductivity is then calculated. Different variants of the algorithm and their combinations with other system parameters are tested: exchange of atomic velocities versus exchange of molecular center-of-mass velocities, different exchange frequencies, molecular models with bond constraints versus models with flexible bonds, united-atom versus all-atom models, and presence versus absence of a thermostat. To help establish the range of applicability, the algorithm is tested on different models of benzene, cyclohexane, water, and n-hexane. We find that the algorithm is robust and that the calculated thermal conductivities are insensitive to variations in its control parameters. The force field, in contrast, has a major influence on the value of the thermal conductivity. While calculated and experimental thermal conductivities fall into the same order of magnitude, in most cases the calculated values are systematically larger. United-atom force fields seem to do better than all-atom force fields, possibly because they remove high-frequency degrees of freedom from the simulation, which, in nature, are quantum-mechanical oscillators in their ground state and do not contribute to heat conduction. 相似文献
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Florian Breitsameter Hans-Peter Schrdel Alfred Schmidpeter Heinrich Nth Susana Rojas-Lima 《无机化学与普通化学杂志》1999,625(8):1293-1300
Ylide Adducts of Pentele Trichlorides Ylides Ph3PCR2 form 1 : 1 adducts with PCl3, AsCl3 und SbCl3. The addition of HCl to dichlorophosphanyl- und dichloroarsanyl ylides also leads to such adducts. In solution the PCl3 adducts 2 are dissociated into ions. For the AsCl3 adducts 3 b and 3 e of triphenylphosphonium ethylide and isopropylide X-ray analyses show distinctly different degrees of transition from a zwitterionic ψ-tbp to a cationic ψ-tetrahedral structure. The SbCl3 adduct 4 b of the triphenylphosphonium ethylide on the other hand forms a rather asymmetric dimer and approaches a square-pyramidal geometry at the antimony atom. The 2 : 1 ylide adducts 11 with PCl3 form in solution the dications (Ph3PCR2)2PCl2+. The 2 : 3 adduct 15 of triphenylphosphonium methylide to AsCl3 also has an ionic structure in the crystal. There are cations (Ph3PCH2)2AsCl2+, which pairwise join with two AsCl3 molecules to form doubly charged supracations in the presence of As2Cl82– as counterions. 相似文献
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氨基羧酸纤维分离富集水中痕量铅镉 总被引:3,自引:0,他引:3
铅、镉是有毒元素,严重危害人体健康,因此水中铅镉的含量历来是水质监测评价中的必测项目。但由于水样中铅镉含量较低,且基体干扰严重,所以测定前必须采取一定的富集与分离方法。本文在原螯合纤维制备的基础上[1,2]改换某些原料[3,4],制备了氨基乙酸纤维滤... 相似文献
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Cs[Na(NH3)6][B10H10]·NH3 was synthesised from cesium and disodium‐decahydro‐closo‐decaborate Na2B10H10 in liquid ammonia, from which it crystallized in form of temperature sensitive colorless plates (triclinic, P1¯, a = 8.4787(7) Å, b = 13.272(1) Å, c = 17.139(2) Å, α = 88.564(1)°, β = 89.773(1)°, γ = 81.630(1)°, V = 1907.5(3) Å3, Z = 4). The compound is the first example of an alkali metal boranate with two different types of cations. The decahydro‐closo‐decaborate dianions [B10H10]2— and the cesium cations form a equation/tex2gif-stack-1.gif[Cs2(B10H10)2]2— layer parallel to the ac plane. These layers are separated by N—H···N‐hydrogen bonded hexamminesodium cations. 相似文献