Investigation of stability and migration mechanism of defects in ZnGeP<sub>2</sub> crystals by density functional theory

ZnGeP<sub>2</sub> crystals are the frequency conversion materials with excellent comprehensive performances in a range of 3–5 μm. However, overlap absorption band and pump wavelength optical parametric oscillator at 8–12 μm limits application performance makes it impossible to achieve far-infrared laser output. In this work, formation energy migration mechanism six kinds defects crystal discussed by density functional theory. The results show that two defective structures <inline-formula><tex-math id="M10">\begin{document}$\rm{V_P}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20220610_M10.jpg"/><graphic xlink:href="22-20220610_M10.png"/></alternatives></inline-formula>and id="M11">\begin{document}$\rm{V_{Ge}}$\end{document}</tex-math><alternatives><graphic xlink:href="22-20220610_M11.jpg"/><graphic xlink:href="22-20220610_M11.png"/></alternatives></inline-formula> difficult form, while four id="M12">\begin{document}$\rm V_{\rm Zn}^ -$\end{document}</tex-math><alternatives><graphic xlink:href="22-20220610_M12.jpg"/><graphic xlink:href="22-20220610_M12.png"/></alternatives></inline-formula>, id="M13">\begin{document}$\rm{Z{n_{Ge}}}$\end{document}</tex-math><alternatives><graphic xlink:href="22-20220610_M13.jpg"/><graphic xlink:href="22-20220610_M13.png"/></alternatives></inline-formula>, id="M14">\begin{document}$ {\rm Ge}_{\rm + $\end{document}</tex-math><alternatives><graphic xlink:href="22-20220610_M14.jpg"/><graphic xlink:href="22-20220610_M14.png"/></alternatives></inline-formula> id="M15">\begin{document}$\rm{ G{e_{\rm Zn}} {V_{\rm Zn}}}$\end{document}</tex-math><alternatives><graphic xlink:href="22-20220610_M15.jpg"/><graphic xlink:href="22-20220610_M15.png"/></alternatives></inline-formula> easy create. When number Ge atoms slightly more than Zn crystals, vacancy id="M16">\begin{document}$\rm xlink:href="22-20220610_M16.jpg"/><graphic xlink:href="22-20220610_M16.png"/></alternatives></inline-formula> form easily antistructure id="M17">\begin{document}$ xlink:href="22-20220610_M17.jpg"/><graphic xlink:href="22-20220610_M17.png"/></alternatives></inline-formula> 10 K, 500 K 600 but id="M18">\begin{document}$ xlink:href="22-20220610_M18.jpg"/><graphic xlink:href="22-20220610_M18.png"/></alternatives></inline-formula> easier id="M19">\begin{document}$ {\text{V}}_{\text{Zn}}^{-} xlink:href="22-20220610_M19.jpg"/><graphic xlink:href="22-20220610_M19.png"/></alternatives></inline-formula> 273 400 K. There is negative correlation between volume expansion rate defect crystal. larger rate, lower is. differential charge shows electron cloud among enhanced Ge<sub>Zn</sub> V<sub>Zn</sub>+Ge<sub>Zn</sub>. lattices when (V<sub>Zn</sub> V<sub>Ge</sub>) (Ge<sub>Zn</sub> Zn<sub>Ge</sub>) joint defects. Comparing defect-free cells, increases significantly, significantly reduced, P does not change Zn<sub>Ge</sub> or Ge<sub>Zn</sub>. spectra 10K there significant from 0.6 2.5 for structures: V<sub>Ge</sub>, V<sub>Zn</sub>, Ge<sub>Zn</sub>, small V<sub>P</sub> Ge<sub>Zn</sub>+V<sub>Zn</sub>. V<sub>Zn</sub> has lowest energy, V<sub>Ge</sub> highest. difficulty migrate depends on space resistance, depend inter-atomic distance. This may be related radius high proportion large low atom