Theoretical Study On Interaction Potential Energy Surface Between Superatoms

Superatoms,as the artificial units at the atomic level,the molecular orbitals of superatoms can exhibit an orbital shape similar to that of electrons in shell of atom.Therefore,superatoms are expected to simulate even replace atoms,and lay the foundation for the bottom-up construction of new functional materials even devices based on the artificial units.Although superatoms have atom-like properties,the interaction characteristics between superatoms is very different from that between atoms themselves because of the superatomic molecular properties.Therefore,the relevant work is urgent and should be implement in a targeted manner.Exploring the interactions between superatoms and understanding their physical mechanisms not only has obvious significance for basic research,but also has important value for further enriching the understanding of material world and realizing the regulation of properties of man-made materials.In the process of interaction between superatoms,a basic aspect is the influence of structural changes on energy.Therefore,we conducted a deep understanding about behavior of interaction between superatoms from the perspective of interaction potential energy surface(PES),and studied the similarities and differences of the PES for inter-superatom and interatom.Furthermore,supermolecules,formed by superatoms,become new units,and the structural properties of interactions between supermolecules are researched.As molecules,superatom is different from atom due to their complex structures,so its potential energy related to not only distance,but also the relative rotation of superatoms.Therefore,the superatomic PES has one more angular dimension than that of atom.We choose the embedded metal fullerene(EMF)superatom Pa@C₂₈,a spherical-like structure,to explore the interaction PES between(Pa@C₂₈)₂,and then compare with the one between atoms.Results show that the PES between superatoms produce crossing behavior between different electronic states similar to the PES between atoms.The superatom rotate around two class of axes,one passing through two central atoms of superatoms and another perpendicular to above axis,and the changes of energy and charge transfer between superatoms are different because of the different rotation axes.The results show that the changes in the maximum energy and charge transfer between superatom caused by the former are 0.33 e V and 10^-2 e,respectively,while the changes caused by the latter are 17 times and 7 times as much as that of the former.All these fully demonstrate the complexity of interaction between superatoms.Moreover,two Pa@C₂₈superatoms combine to form the supermolecule(Pa@C₂₈)₂whose electronic structure is a closed shell,thus the structural characteristics of interaction between two(Pa@C₂₈)₂ are studied.First-principle theoretical calculations show that five isomeric structures of(Pa@C₂₈)₄ are discovered and their properties are explored.Energy decomposition analysis(EDA)shows that four interaction structures are physical adsorption structures,and the interactions between supermolecules are all dominated by dispersion interaction.That is,adsorption between two(Pa@C₂₈)₂ is mainly through weak interaction.The other is a chemical adsorption structure with the electronic state of spin-polarized singlet state,where the orbital interaction plays a major role in the covalent single bond connection between supermolecules,thus it forms a stable one-dimensional chain structure.Interestingly,further interaction analysis shows that the physical adsorption structures are more stable than the chemical adsorption structure,so the system tends to form a weak interaction mode between the two supermolecules.This research has important reference significance for the assembly of supermolecules as units.Through the above theoretical researchs at atomic level,we explored the interaction between superatoms from the perspective of PES,and revealed the complex interactions between superatoms.On this basis,the supermolecule formed by superatoms,as the unit,interaction structures between supermolecules was studied.The interesting phenomenon that physical adsorption structures are more stable than chemical adsorption structure are found.These findings can be explained by the superatomic electronic structures,which contribute to regulate the characteristics of interaction.In the future,we hope these laws and understandings can inspire researchers to continue to explore the footprint of superatomic interactions,and promote the regulation of superatomic structures and functional properties,as well as realize the improvement of related science and technology such as device design based on superatoms and even supermolecules.