| In order to looking for the special properties of the practical application in the nitride materials,our self-developed CRYSTREE（Crystal Structure Prediction based on Machine Learning）software help,combining with the foundation of the first principles density functional perturbation theory,the Mo-N and Ce-N system under high pressure Structure search,research of the Structure of binary nitrides at high pressure,dynamic stability,phonon properties,energy density,superconductivity.The work for the future looking for new high energy density materials provides a theoretical guidance.The main work is as follows:（1）Using CRYSTREE search crystalline structure of the software.This is a software based on machine learning algorithm,after other relevant work of the project group has proved its excellent algorithm performance and the rationality of the results.We first went to CRYSTREE input random initial structure symmetry,then carries on the DFT optimization,and enthalpy machine learning collection and analysis,and then control enthalpy of convergence and calculation step length,after comprehensive assessment result in the most stable structure.To compare we still in CALYPSO software did a control group,the results found CRYSTREE in guarantee under the premise of consistent,do have more efficient,the advantages of low energy consumption.（2）With the help of CRYSTREE,we obtained several Mo-N and the stability of the structure under the Ce-N system,and based on density functional perturbation theory of phonon density of states of phonon dispersion.Then use WIEN2K calculate their band and electronic density of states,has found that some of the structure from insulator to weak gold finally won gold attribute the behavior of the conclusion part of the structure with superconductivity is obtained.Finally,through XCRYSDEN and FERMISURFER tools to implement the Fermi surface rendering.（3）Based on the results of QUANTUM ESPRESSO get chemical equation of the transformation process,the energy needed to draw material before and after the change.Coupled with the quality of each formula of nitrides get quality energy density,through conversion can be obtained at the same time the volume energy density.Final conclusion is P4/mmm-Mo N2under 50 GPa pressure superconducting（Tc=29.04 K）,Pm-3m-Mo N6have high hardness（Hv=63.24 GPa）and energy density（gravimetric energy density=4.77 k J/g）.R-3-Ce N8superconducting（Tc=31.72 K）under 180 GPa pressure.At the same time,it has good hardness（Hv=43.97 GPa）and energy density（gravimetric energy density=3.81 kJ/g）. |
