Impact of Transition Metal Cations on the 29 Si NMR Signal in Metal Oxide Glasses: A DFT Case Study of Hafnia Silica Glass
Impact of Transition Metal Cations on the 29 Si NMR Signal in Metal Oxide Glasses: A DFT Case Study of Hafnia Silica Glass
复制标题
过渡金属阳离子对金属氧化物玻璃中 29 Si NMR 信号的影响：氧化铪二氧化硅玻璃的 DFT 案例研究
DOI：
10.1021/acs.jpcc.7b06094
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Kroll, Peter
中科院分区：
文献类型：
--
作者：
Ponomarev, Ilia;Kroll, Peter
我们通过结构建模和密度泛函数理论（DFT）中的量规不变投影增广波（GIPAW）方法研究了29si核磁共振（NMR）中钠-二氧化硅和铪-钠-二氧化硅玻璃的化学位移δ等。通过熔体淬火和从头算分子动力学模拟，建立了Na2O: sio2摩尔比为1:2和1:3、铪含量为0-10 mol %的钠硅玻璃模型。通过将计算的化学位移与结构数据相关联，我们建立了钠硅玻璃中Q2、Q3和q4单元的角相关函数。在钠-硅玻璃中加入半氟化氢会导致6配位的Hf被桥接的O包围，从而避免了Hf中心八面体之间的直接连接。Hf对可以从29si NMR分析中收集到的结构信息产生了深刻的影响：与Si的第二配位中的每个Hf都会使Si - o - X （X = Si, Hf）角度的角相关函数偏移3-5 ppm。因此，q2和q3单元的核磁共振信号可能会重叠，这取决于Si周围Hf的数量。通过用H代替Na，我们将玻璃模型转化为溶胶-凝胶衍生的HfO2-SiO2模型。Hf对29si化学位移的深刻影响要求重新解释在铪-硅玻璃中观察到的29si核磁共振峰。
We investigate29Si nuclear magnetic resonance (NMR) chemical shifts δisoof soda-silica and hafnia-soda-silica glass models by structural modeling and the gauge-invariant projector augmented wave (GIPAW) method within density functional theory (DFT). Models of soda-silica glasses with molar ratios Na2O:SiO2of 1:2 and 1:3 and hafnia content of 0–10 mol % are generated via a melt-quench procedure and ab initio molecular dynamic simulations. By correlating computed chemical shifts with structural data we establish angular correlation functions for Q2, Q3, and Q4units in soda-silica glasses. Addition of hafnia to soda-silica glasses results in 6-coordinated Hf surrounded by bridging O under avoidance of direct linkages between Hf-centered octahedra. Hf impacts the structural information that can be gathered from29Si NMR analysis profoundly: each Hf in second coordination to Si shifts the angular correlation function for Si–O–X (X = Si, Hf) angles by 3–5 ppm. Hence, NMR signals of Q2and Q3units may overlap depending on the number of Hf surrounding Si. By substituting H for Na we convert the glass models into models of sol–gel derived HfO2–SiO2. The profound impact of Hf on the chemical shift of29Si calls for a reinterpretation of29Si NMR peaks observed for hafnia-silica glasses.