Zirconium dioxide, or zirconia, is a common and useful ceramic with a wide range of applications, from fuel cells to odontology. Its phase diagram is simple and well understood, having a structure which is monoclinic at temperatures up to 1500 K, tetragonal up to 2700 K and cubic up to 3000 K. Zirconia is rarely used in its pure form, being typically doped with ${\text{Y}}_2{\text{O}}_3$, MgO or ${\text{TiO}}_2$, and in this regime its phase diagram becomes much more complex. In this context, ab initio molecular dynamics (AIMD) can provide a detailed atomistic description of the phase diagram of this system, accurately describing its stable phases and transition regions. In this work, 3 mol-% ${\text{Y}}_2{\text{O}}_3$ (3YSZ) crystals doped with different Ti contents were studied at the density-functional level. For Ti contents varying from 0 to 30 at%, a global search algorithm was first used to explore the 0 K potential-energy surface and determine the most stable sites for the added Ti atoms. It was found that, at low Ti compositions $X_{\text{Ti}}$, small ${\text{TiO}}_2$ clusters form, followed by ${\text{TiO}}_2$ channels and infinite ${\text{TiO}}_2$ planes at larger $X_{\text{Ti}}$ values, and that the highest stability is achieved at 9% Ti. AIMD simulations within the isothermal-isobaric NPT ensemble were then performed to characterize the temperature-dependent phase changes as a function of the Ti content, where it was found that the Ti-doped structures presented considerably smaller volume changes near the phase-change critical temperatures. These findings suggest that YSZ materials doped with a small amount of Ti are both energetically and kinetically more stable than the undoped counterparts, in the ideal proportion of 3% ${\text{TiO}}_2$ for every 1% ${\text{Y}}_2{\text{O}}_3$ doping.

中文翻译：

---

温度引起的相变的从头算的描述：氧化锆和Ti-Y共掺杂氧化锆的情况

二氧化锆或氧化锆是一种常见且有用的陶瓷，具有从燃料电池到牙科学的广泛应用。其相图简单易懂，其结构在最高1500 K的温度下为单斜晶，在最高2700 K的温度下为四方晶，在最高3000 K的立方下为晶状体。氧化锆很少以其纯净形式使用，通常掺杂有${\text{ÿ}}_2{\text{Ø}}_3$，MgO或 ${\text{二氧化钛}}_2$，在这种情况下，其相图变得更加复杂。在这种情况下，从头算分子动力学（AIMD）可以提供该系统相图的详细原子描述，准确描述其稳定的相和过渡区域。在这项工作中，3摩尔％${\text{ÿ}}_2{\text{Ø}}_3$在密度泛函能级研究了掺杂不同Ti含量的（3YSZ）晶体。对于Ti含量从0到30 at％的变化，首先使用全局搜索算法探索0 K势能表面并确定添加的Ti原子的最稳定位点。发现在低Ti含量下$X_{\text{钛}}$， 小的 ${\text{二氧化钛}}_2$ 集群形式，其次是 ${\text{二氧化钛}}_2$ 渠道和无限 ${\text{二氧化钛}}_2$ 大飞机 $X_{\text{钛}}$值，并且在9％Ti时达到最高的稳定性。然后在等温-等压NPT集合体中进行AIMD模拟，以表征随温度变化的相变与Ti含量的关系，在此发现，掺杂Ti的结构在相变临界温度附近的体积变化小得多。这些发现表明，掺有少量Ti的YSZ材料在能量和动力学上都比未掺杂的TiSZ材料更稳定，理想比例为3％。${\text{二氧化钛}}_2$ 每1％ ${\text{ÿ}}_2{\text{Ø}}_3$ 掺杂。