A Qtaim Perspective Of Potential Energy Surface Using Quantum Topology Phase Diagrams

This dissertation is devoted to perspective of potential energy surface using quantum topology phase diagrams within the ‘quantum theory of atoms in molecules’ framework. All data come from two parts, namely, all calculations are performed with Gaussian 09 package and the topological analysis for total electronic charge density distribution ρ(r) of molecules carried out with AIMALL. The thesis contains six relatively independent chapters.In chapter 1, a brief introduction to relevant theoretical and computational background and computation software is provided.In chapter 2, a mainly introduction a summary of some of the major basic concepts of QTAIM, such as: critical points, bond ellipticity, bond path, metallicity, local energy density and we developed the Conceptual Quantum Topology, especially, the quantum topology phase diagrams.In chapter 3, we explore and expand potential energy surface of Si6Li6 using a new quantum topology phase diagram within QTAIM framework, seventeen new unique topologies were found. Two types of 3-D quantum topology phase diagram were created to accommodate the presence of non-nuclear attractors(NNAs) to ensure unique solutions of the Poincaré-Hopf relation. Revealed the linear relationship between the types of NNAs and polarizability and energetic stability, the correlation of the fit is 0.912 and the exponential relationship between local energy density with longest bond-path include Si-NNA or Li-NNA and the metallicity, the correlation of the fit is 0.914. Lowest polarizabilities explained in terms of the Si-NNA BCPs acquiring ‘Lithium character’.In chapter 4, water clusters(W = H2O)n(7-10) is analyzed employing the scalar fields of molecular electron density(MED) and molecular electrostatic potential(MESP). The spanning MED QTPD with upper and lower bounds is constructed, demonstrated the migration of the position of the global minimum on the spanning MED QTPD from the lower bound to upper bound as the Wn(4-10) cluster grows in size. Differences in the structure of the MED QTPD are found between the clusters containing even versus odd monomers for Wn, n = 7-10. A ‘hybrid’ spanning QTPD is created from a new chemical relation bHB + l ≥ 2n for Wn that relates the number of hydrogen-bond bond critical points(b HB) with the number of oxygen lone pairs exclusively specified by the negative valued MESP(3, +3) critical points(l).In chapter 5, a conclusion and future work about W5 translate state were listed in this part.