STRUCTURAL TRANSFORMATION OF QUARTZ AT HIGH-PRESSURES
STRUCTURAL TRANSFORMATION OF QUARTZ AT HIGH-PRESSURES
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DOI：
10.1038/353344a0
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发表时间：
1991-09-26
期刊：
影响因子：
64.8
通讯作者：
CHELIKOWSKY, JR
中科院分区：
文献类型：
--
作者：
BINGGELI, N;CHELIKOWSKY, JR
α-石英是最常见的四面体配位二氧化硅多晶型物之一，它在高压下的行为一直是几项实验研究的主题。 在室温下，观察到逐渐的压力诱导的非晶化（在约25-35 GPa下）1，2，随后在较高的压力下（高于60 GPa）转变为晶体八面体配位的“金红石状”结构3。这些转变的驱动力还没有得到很好的理解。 我们在这里报告的第一性原理计算的高压结构的α-石英，这表明压力引起的转变的氧亚晶格的体心立方结构的电子和结构特性。 立方堆积的主要特征是在30 GPa下出现，而理想的形式是在大约60 GPa下实现的。 立方亚晶格的形成有利于涉及Si配位变化的结构转变。 在氧体心立方晶格中，硅离子沿着结构的空通道的小位移足以将α-石英转变为具有混合的四重/六重配位的结构，或者对于较大的硅位移，转变为纯六重配位的结构。 这一描述与分子动力学模拟4中的非晶化压力以上的混合Si配位的中间结晶相的证据一致，并且也可以解释在更高压力下向六重结晶结构的转变。
THE behaviour of alpha-quartz, one of the most common tetrahedrally coordinated silica polymorphs, at high pressures has been the subject of several experimental studies. At room temperature, gradual pressure-induced amorphization is observed (at about 25-35 GPa) 1,2, followed at higher pressures (above 60 GPa) by a transformation to a crystalline octahedrally coordinated 'rutile-like' structure 3. The driving force for these transformations is not well understood. We report here first-principles calculations of the electronic and structural properties of the high-pressure structure of alpha-quartz, which show a pressure-induced transformation of the oxygen sublattice to a body-centred cubic structure. The main features of cubic packing are present at 30 GPa, and the ideal form is achieved at about 60 GPa. The formation of the cubic sublattice facilitates structural transformations involving a change in Si coordination. In the oxygen body-centred cubic lattice, a small displacement of Si ions along the empty channels of the structure is sufficient to transform alpha-quartz either to a structure with mixed fourfold/sixfold coordination or, for a larger silicon displacement, to a purely sixfold-coordinated structure. This description is consistent with the evidence of intermediate crystalline phases with mixed Si coordination above the amorphization pressure in molecular-dynamics simulations 4, and can also explain the transformation to a sixfold crystalline structure at higher pressure.