The condensed behavior of polymer fluids were studied based on the van der Waals interaction. By comparing the phase diagram of pure polymer fluids and that of van der Waals non-ideal fluids, it is found that (1) pure...The condensed behavior of polymer fluids were studied based on the van der Waals interaction. By comparing the phase diagram of pure polymer fluids and that of van der Waals non-ideal fluids, it is found that (1) pure polymer fluids show a similar phase diagram to van der Waals non-ideal fluids; (2) the differences between the phase diagrams were caused by the difference of chain lengths. It is explained that why the vapor pressure of polymer is hard to detect and why the negative pressure can exist in polymer liquids. It is also found that some scaling relations exist between the reduced critical pressure and the chain length, and the reduced critical volume and the chain length.展开更多
Benzene dimer （bz2） is the simplest prototype of the π-π interactions. Such interactions are ubiquitous in diverse areas of science and molecular engineering. In the present work, we have made assessment on some m...Benzene dimer （bz2） is the simplest prototype of the π-π interactions. Such interactions are ubiquitous in diverse areas of science and molecular engineering. In the present work, we have made assessment on some modern density functional methods including B97-D, BLYP-D3, M06-2X, XYG3, and force field models including CHARMM, AMBER, MM3, AMOEBA on six important interaction modes of bz2. Our results not only highlight the usefulness of these cost-effective methods, which can be used as economic substitutes of the expensive CCSD（T） for complex real-world systems, but also indicate their weakness in the description of the π-π interactions, which points to the future direction for further improvements.展开更多
文摘The condensed behavior of polymer fluids were studied based on the van der Waals interaction. By comparing the phase diagram of pure polymer fluids and that of van der Waals non-ideal fluids, it is found that (1) pure polymer fluids show a similar phase diagram to van der Waals non-ideal fluids; (2) the differences between the phase diagrams were caused by the difference of chain lengths. It is explained that why the vapor pressure of polymer is hard to detect and why the negative pressure can exist in polymer liquids. It is also found that some scaling relations exist between the reduced critical pressure and the chain length, and the reduced critical volume and the chain length.
基金Acknowledgments： This work was supported by the National Natural Science Foundation of China （No.91027044） and the Ministry of Science and Technology （No.2011CB808505）.
文摘Benzene dimer （bz2） is the simplest prototype of the π-π interactions. Such interactions are ubiquitous in diverse areas of science and molecular engineering. In the present work, we have made assessment on some modern density functional methods including B97-D, BLYP-D3, M06-2X, XYG3, and force field models including CHARMM, AMBER, MM3, AMOEBA on six important interaction modes of bz2. Our results not only highlight the usefulness of these cost-effective methods, which can be used as economic substitutes of the expensive CCSD（T） for complex real-world systems, but also indicate their weakness in the description of the π-π interactions, which points to the future direction for further improvements.
