Understanding the mechanism of the insulator–metal transition (IMT) in VO₂ is a necessary step in optimising this material's properties for a range of functional applications. Here, Rietveld refinement of synchrotron X-ray powder diffraction patterns is performed on thermochromic V_1−xW_xO₂ (0.0 ≤ x ≤ 0.02) nanorod aggregates over the temperature range 100 ≤ T ≤ 400 K to examine the effect of doping on the structure and properties of the insulating monoclinic (M₁) phase and metallic rutile (R) phase. Precise measurement of the lattice constants of the M₁ and R phases enabled the onset (T_on) and endset (T_end) temperatures of the IMT to be determined accurately for different dopant levels. First-principles calculations reveal that the observed decrease in both T_on and T_end with increasing W content is a result of Peierls type V–O–V dimers being replaced by linear W–O–V dimers with a narrowing of the band gap. The results are interpreted in terms of the bandwidth-controlled Mott–Hubbard IMT model, providing a more detailed understanding of the underlying physical mechanisms driving the IMT as well as a guide to optimising properties of VO₂-based materials for specific applications.

中文翻译：

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用Rietveld精炼和理论模型表征W掺杂的VO2纳米棒聚集体中与温度有关的M1至R相变

了解VO _2中绝缘体-金属过渡（IMT）的机理是在一系列功能应用中优化该材料性能的必要步骤。在此，被热致变色V执行的同步辐射X射线粉末衍射图案的Rietveld精化_{1- X} w ^ _X Ô ₂（0.0≤ X ≤0.02）纳米棒的聚集体的温度范围内100≤ Ť ≤400 K至审查关于掺杂的效果绝缘单斜（M ₁）相和金红石（R）相的结构和性能。精确测量M ₁和R相的晶格常数可实现起始（T _on）和IMT的_端温度（T _end），可以针对不同的掺杂水平精确确定。第一性原理计算表明，观察到的T _on和T _end随W含量的增加而降低是Peierls型V–O–V二聚体被带隙变窄的线性W–O–V二聚体所代替。根据带宽控制的Mott–Hubbard IMT模型来解释结果，从而提供了对驱动IMT的基本物理机制的更详细了解，并为针对特定应用优化基于VO ₂的材料的性能提供了指南。