Letter. Identification of hydrogen defects linked to boron substitution in synthetic forsterite and natural olivine
Letter. Identification of hydrogen defects linked to boron substitution in synthetic forsterite and natural olivine
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DOI：
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发表时间：
2014
期刊：
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通讯作者：
J. Hermann
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作者：
J. Ingrin;I. Kovács;E. Deloule;E. Balan;M. Blanchard;S. Kohn;J. Hermann
本文给出了合成镁橄榄石和天然橄榄石中B和H偶联取代的实验和理论证据。非均相掺B合成镁橄榄石晶体中3704 cm-1(//z)、3598 cm-1(//x，y)和3525 cm-1(//x)处的氢键强度与离子探针测量的B浓度带相吻合。10B和11B分别在1301 cm-1(//x)和1207 cm-1(//z)处和1256 cm-1和1168 cm-1处出现BO_3基团的两个反对称伸缩振动。通过量子力学计算得到了混合(B，H)缺陷的微观模型，该模型解释了实验观测结果。BO_3基团位于空位Si的(O_3-O_1-O_3)面上，H原子在剩余的顶端与O_2原子成键。在来自巴基斯坦的天然橄榄石样品中，与v3BO3振动相关的相同OH带的出现证实了自然界中存在这种缺陷。在橄榄石和镁橄榄石中，这三个诊断的OH带可以作为与硼取代有关的H的特征，从而定量地分析了它们对H-缺陷的贡献。
Abstract Experimental and theoretical evidence for the coupled substitution of B and H in synthetic forsterite and a natural olivine is presented. The intensities of OH bands at 3704 cm-1 (//z), 3598 cm-1 (//x,y), and 3525 cm-1 (//x) in a heterogeneous B-doped synthetic forsterite crystal matches the zoning of B concentration measured by ion probe. The two anti-symmetric stretching vibrations of BO3 groups occur at 1301 cm-1 (//x) and 1207 cm-1 (//z) for the 10B and at 1256 and 1168 cm-1 for the 11B isotope. A microscopic model of the mixed (B,H) defect that accounts for experimental observations is obtained from quantum mechanical calculations. The BO3 group lies on the (O3-O1-O3) face of the vacant Si site and the H atom is bonded to the O2 atom at the remaining apex. The occurrence of the same OH bands associated with v3 BO3 vibrations in a natural olivine sample from Pakistan confirms the occurrence of this defect in nature. The three diagnostic OH bands can be used as a signature of H associated with boron substitution in olivine and forsterite, leading to a quantitative analysis of their contribution to H-defects.