Study On The Structure And Electronic Properties Of ?Li₃n?_nH₂?n=2-6? And ?Tih₂?_5n?n=2-11? Nanoclusters

With the continuous consumption of global petroleum resources,the shortage of petroleum resources and the problem of petroleum pollution are becoming more and more serious.Therefore,the development of a new type of clean energy has become an important issue facing the world.Hydrogen is an ideal energy carrier and is considered for future transportation,such as automotive applications.Under these circumstances,the storage of hydrogen is one of the major challenges in developing a hydrogen economy.Li3N hydrogen storage system has been the subject of hydrogen storage research due to its high hydrogen storage capacity,and TiH2 has recently received widespread attention as a hydrogen storage medium.The theoretical calculation plays an important role in understanding the mechanism of hydrogen storage.At the same time,nanoscale reactions can reduce the conditions under which the reactions proceed.Therefore,the study of different types of hydride cluster structures is crucial.In this paper,based on the density functional theory,combined with Coalescence Kick(CK)and artificial bee colony algorithm search and obtained(Li3N)nH2(n=2-6)and(TiH2)5n(n=2-11)clusters Probably the lowest energy structure,and its structure and electronic properties were studied.Through our analysis,we have the following two conclusions.Through our analysis,we have the following two conclusions.(1)By calculating the total binding energy of(Li3N)nH2(n=2-6)clusters,we find that the total energy of all clusters is negative,which indicates the stability of clusters.At the same time,we analyzed the bond length information in the cluster.Through NBO charge and electron local function analysis,we find that Li-N bonds exhibit ionic bond characteristics,and N-H bonds exhibit covalent bond characteristics.By analyzing the vibration frequency in clusters,we found that among all clusters,peaks of different degrees appeared in two areas.Among them,the main vibration mode is the bending vibration between L-N-H in the range of 52.80-1135.30cm-1,and the stretching vibration of the N-H bond in the range of 3360.76-3464.40cm-1.(2)By comparing the average binding energy of(TiH2)5n(n=2-11),the average binding energy of all clusters is negative,and large clusters(35?n?55)are found to be smaller than small ones Clusters(10<n?35)are more stable.At the same time,we also calculated the bond length and coordination number of the cluster and compared with the TiH2 crystal,which further showed the rationality of the cluster structure we obtained.By calculating the HOMO-LUMO energy gap of the cluster,we find that as the size of the cluster increases,its chemical activity gradually increases.At the same time,the HOMO-LUMO energy gap value of the cluster(TiH2)55 is the lowest,which indicates that(TiH2)55 has a relatively high chemical activity.Through the density of states of Ti50H100,Ti35H70,Ti10H20 clusters and COHP analysis,we found that there is a bond between Ti and H between-9eV and-3eV,and there is no bond near the Fermi level.Finally,by analyzing the HOMO,LUMO and bonding orbitals of Ti50H100,Ti35H70,Ti10H20,we found that the Ti10H20 cluster formed a large ? bond at the highest peak of bonding.