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71.
Aidin Bahrami Sirous Yourdkhani Mehdi D. Esrafili Milad Bahrami Nasser L. Hadipour 《Structural chemistry》2013,24(4):1273-1279
Density functional theory calculations at the B3LYP/6-31G(d) and B3LYP/6-31+G(d) levels were carried out for the adsorption of NH3 on three symmetric isomers of B80 {C 1, T h, I h}. To investigate the binding features of B80 isomers with NH3, different studies including the structural and electronic parameters, the 14N electric field gradient tensors and the atoms in molecules (AIM) properties were considered. The calculated parameters by these investigations can be used as powerful tools to find out some of the unknown aspects of electronic structures of the boron buckyball and its isomers. According to previous studies, boron buckyball as an amphoteric and a hard molecule has two distinct reactive sites defined as cap and frame which act as an acid and a base, respectively. Regarding the obtained results in this study, all the isomers had the same exposure when NH3 molecule reacted with the external wall of B80. For instance, the stability of N–B bond in the cap site was significantly more than the stability of N–B bond in the frame. Moreover, the adsorption of NH3 on frame site showed a considerable reduction in HOMO–LUMO energy gap. According to AIM theory, an electrostatic nature was observed for N–B interaction. Concerning the selected isomers of buckyball, the capability of the NH3–B80 complexes to localize electron at the N–B bond critical points depend on the reaction sites significantly. In general, 14N nuclear quadruple coupling constants and asymmetry parameter reveal a remarkable effect of NH3 adsorption on electronic structure of the B80. 相似文献
72.
Nonlinear Dynamics - A nonlinear mathematical model is developed in the time domain to simulate the behaviour of two identical flexibly mounted cylinders in tandem while undergoing vortex-induced... 相似文献
73.
Dehghan Maziar Jamalabad Milad Tajik Rashidi Saman 《Journal of Thermal Analysis and Calorimetry》2020,141(5):1943-1950
Journal of Thermal Analysis and Calorimetry - The convection heat transfer inside a tube filled with a porous material under the constant heat flux thermal boundary condition which is widely used... 相似文献
74.
76.
We investigate the asymmetries arising due to electromagnetic interactions in largeP
T pion inclusive processes. The hardqcd processes that contribute to such asymmetries areq+g→q+γ,q+q→g+γ etc. which are suspected to be substantial, as indicated by theqcd predictions for a significant and increasingγ/π
o ratio at largeP
T. We calculate the expected isospin related asymmetries and propose tests that might detect them. Our estimates indicate that
the effects are much smaller than may be naively expected. We also observe a remarkable scaling of asymmetries in the variableP
T/(s)1/2. 相似文献
77.
78.
We present a novel algorithm to integrate property densities over the volume of a quantum topological atom. Atoms are grown outward, starting from a sphere centered on the nucleus, by means of a finite element meshing algorithm. Bond critical points and ring critical points require special treatment. The overall philosophy as well as intricate features of this meshing algorithm are given, followed by details of the quadrature over the finite elements. An effort has been made to design a streamlined and compact algorithm, focusing on the core of challenges arising in tracing the electron density's gradient vector field. The current algorithm also generates a new type of pictures that can be a Graphical User Interface. Excellent integration errors, L(Omega), are obtained, even for atoms with (narrow) tails or sharp corners. 相似文献
79.
Classical force fields describe the interaction between atoms that are bonded or nonbonded via simple potential energy expressions. Their parameters are often determined by fitting to ab initio energies and electrostatic potentials. A direct quantum chemical guide to constructing a force field would be the atom-atom partitioning of the energy of molecules and van der Waals complexes relevant to the force field. The authors used the theory of quantum chemical topology to partition the energy of five systems [H2, CO, H2O, (H2O)2, and (HF)2] in terms of kinetic, Coulomb, and exchange intra-atomic and interatomic contributions. The authors monitored the variation of these contributions with changing bond length or angle. Current force fields focus only on interatomic interaction energies and assume that these purely potential energy terms are the only ones that govern structure and dynamics in atomistic simulations. Here the authors highlight the importance of self-energy terms (kinetic and intra-atomic Coulomb and exchange). 相似文献
80.
The construction of a high-rank multipolar force field (for peptides) is a complex task, leading to several intermediate questions in need of a clear answer. Here we focus on the convergence of the (electrostatic) multipolar expansion at medium and long range. Using molecular electron densities, quantum chemical topology (QCT) defines the atoms as finite volumes, each endowed with multipole moments. The terms in the multipole expansion are grouped according to powers of the internuclear distance, R(-L). Given two atom types at a given distance, we determine which rank (L) is necessary for the electrostatic energy to converge to the exact interaction energy within a certain error. With this information, the rank of the expansion for each interaction can be adapted to the required accuracy and the available computing power. 相似文献