First-principles Study Of Electron And Elastic Properties Of Zr₂si And Zr_1-xNb_x

Zirconium and its alloys are of great interest due to their unique properties andpotential applications in many fields. Zr₂Si alloy is a kind of aerospace-materials becauseof its lower density, and Zr_1-xNb_xalloys are important artificial bones for their superiorhigh strength-to-weight ratio. In this work, firstly, the structural, elastic, and electronicproperties of Zr₂Si alloy under pressure are investigated by first-principles calculations.The calculated results of enthalpy of formation, density of states and charge densitydistribution unraveled that （1） Zr₂Si is a conductor,（2） there are ionic, covalent andmetallic bondings in the crystal,（3） the higher the pressure, the more stability the phase is.Through investigating the pressure dependence of elastic parameters we found that atambient pressure, Zr₂Si alloy behaves in a brittle manner, whereas, at15GPa there is atransformation between the brittle and the ductile. We also demonstrated that Zr₂Si alloy iselastic anisotropy. At ambient pressure, compressing along the c-axis is larger than alongthe a-axis. At about3.5GPa, it transformed to compressing along the a-axis is larger thanalong the c-axis. The novel phenomenon closely related to the distributions of electrons inthe p orbital. Secondly, we explored the elastic and electron properties of Zr_1-xNb_xbinaryalloys with both ordered and disordered modeling methods. The calculated results shownthat the C₄₄of Zr_1-xNb_xis found to be undervalued from the first-principles calculations;the physical origins attribute to the special density of states and Fermi surfaces of thealloys. Besides, we unraveled that the C₄₄obtained by disordered method is superior tothat obtained by ordered method. Compared to the ordered method, the disordered methodnot only shows an increase in the C₄₄of Zr_1-xNb_xwith decrease in x from0.75to0.5butalso shows the negative deviation for x=0.25from the increasing trend of C₄₄resultingfrom the softening in the body-centered cubic structure. Moreover, we found that theYoung’s modulus of Zr_0.75Nb_0.25is in excellent agreement with that of human bones in the[010] direction. This work is of significant importance in the field of “super alloys” andartificial bones.