It can be seen from Table 2.6 that the frontier orbital energy of pyrite and xanthate | ΔE 2 | is the largest (0.708 eV), followed by marcasite (0.420 eV), and the smallest one is that of pyrrhotite (0.228 eV), which indicates that the interaction between xanthate and marcasite is stronger than that of pyrite, so the floatability of marcasite is better than pyrite. The flotation test shows that by using xanthate as collector, the floatability of the three iron sulfide minerals is in the order of marcasite > pyrite > pyrrhotite. The product of xanthate interacting with three minerals: marcasite, pyrite, and pyrrhotite, is the same as dixanthogen. Δ E 1 = | E HOMO Mineral − E LUMO O 2 | Δ E 2 = | E HOMO xanthate − E LUMO Mineral | In the industrial operation, when the ore contains pyrrhotite, oxygen will react with pyrrhotite preferentially, thus consuming a large amount of oxygen in the pulp, leading to the poor floatability of other sulfide minerals. The spin DOS suggests that pyrite and marcasite are low-spin state, while pyrrhotite is spin polarized, so the oxygen molecule interacts easier with pyrrhotite than pyrite and marcasite. It can be seen from the oxygen molecular orbital that there are two lone pair electrons in two antibonding π orbitals, so the oxygen molecule is paramagnetic. Experimental results shown in Figs.2.12 and 2.13 suggest that the order of oxidation for iron sulfides is pyrrhotite > marcasite > pyrite.
![homo vs lumo homo vs lumo](https://www.differencebetween.com/wp-content/uploads/2018/08/Difference-Between-Homo-and-Lumo-fig-1.png)
It is found that |ΔE 1|, the difference between pyrrhotite HOMO and oxygen LUMO (0.417 eV), is the smallest, followed by marcasite (1.054 eV) and pyrite (1.685 eV), suggesting that the interaction of pyrrhotite with oxygen is the strongest, followed by marcasite, and the interaction of pyrite with oxygen is the weakest. In addition, the products of xanthate adsorbing on pyrite, marcasite, and pyrrhotite are all dixanthogen, so butyl dixanthogen is used to calculate FMO. Table 2.6 indicates that oxidation occurs between HOMO of mineral and LUMO of oxygen, and interaction of xanthate with mineral occurs between HOMO of xanthate and LUMO of mineral. Instead, it is more correct to speak of potential of electrolyte reduction at negative potentials, and of potential of solvent oxidation at positive potentials.FMO suggests that the smaller the absolute ΔE between HOMO and LUMO, the stronger the interaction. In this opinion we provide a correct thermodynamic representation for the electrochemical stability of the electrolyte, based on redox potentials and Fermi level of the electron in solution, and demonstrate that the use of terms HOMO and LUMO should be avoided when talking about the electrochemical stability of electrolytes. Presence of electrolytes and other molecules can also significantly affect the redox potentials of the solvent leading to offset as high as 4 eV from the HOMO energies. While redox potentials in some cases show strong correlation with HOMO energies, the offset can be of several eVs.
#HOMO VS LUMO FREE#
On the other hand, redox potentials are directly related to the Gibbs free energy difference of the reactants and products.
![homo vs lumo homo vs lumo](https://i.ytimg.com/vi/l3Oq0rAejiU/maxresdefault.jpg)
HOMO and LUMO are concepts derived from approximated electronic structure theory while investigating electronic properties of isolated molecules, and their energy levels do not indicate species participating in redox reactions. A widespread misconception in the lithium ion battery literature is the equality of the energy difference of HOMO and LUMO of the solvent with the electrochemical stability window.