The Design And Modulation For New-type Two-dimensional Materials From First-principles Calculation

Nano-science and nanotechnology have promoted the development of moderntechnology and they have played an important role on our daily life. Among of thosenanomaterials, atomic thick two-dimensional materials have attracted a broad interestsince the discovery of graphene. Those materials usually hold special electronicproperties and they may play a key role on the future science and technology. Thus, itis important to research the properties of these and design new two-dimensionalmaterial with novel properties. In this thesis, I have researched the properties andelectron transfer of some two-dimensional materials, also designed newtwo-dimensional material with novel properties. All the results are based onfirst-principles calculation within density functional theory. The main research resultsare list as follows:1. I have researched the reduction progress of graphene oxide with alkaline-earthmetals calcium. Reduction of graphene oxide is a simple way to produce graphene.However, commonly used reduction agents have shortcomings to reduce grapheneoxide. In the thesis, we find that calcium is highly effective to remove oxygen groups,and also can heal the defects forming during the reduction. Calcium serves as anelectron reservoir of high electron chemical potential to force electron transfer to thegraphene oxide. Moreover, calcium even can reduce the oxygen groups which cling tothe edges firmly. Especially for the half-tearing edge with a joint point, calcium canzip the edge to form a bigger graphene after reduction oxygen groups. 2. Based on the strong ability to transfer electron for metal, we designed a newsandwich structure MoB4and MgB6. Among the two structures, metals transferelectrons to electron-deficient boron honeycomb and born kagome to stabilize thesetwo structures. The designed two structures hold novel properties. For example, thesuggested MoB4has two Dirac cones approach Fermi levels and the suggested MgB6holds electron-phonon coupling and hydrogen storage properties.3. Based on the two-dimensional material MoS2, I designed series of two-dimensionalmaterial like that in V-Metal-VII with dipole. Also the potential application inoptoelectronics is shown in this thesis.4. I have researched the structure and energy of metal Hf honeycomb single layer andmulti layers in the Ir substrate. The ferromagnetism of isolated Hf honeycomb isshown. Furthermore, a possible growth mechanism for multi Hf layers is suggested inthis thesis. From the energetic view, in the first and second layers, the Hf layer istended to form honeycomb structure. Thereafter, the Hf layer is tended to formtriangle lattice. Thus, the structure is related to the layers during the growth progressof molecular beam epitaxy.