A shell model for the simulation of rhombohedral carbonate minerals and their point defects
A shell model for the simulation of rhombohedral carbonate minerals and their point defects
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DOI：
10.2138/am-2000-0121
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发表时间：
2000-01-01
影响因子：
3.1
通讯作者：
Cygan, RT
中科院分区：
文献类型：
--
作者：
Fisler, DK;Gale, JD;Cygan, RT
为了更好地模拟方解石和相关的菱面体碳酸盐矿物的结构，氧离子的电子极化被明确地纳入到壳模型中。钙离子和碳酸盐分子离子组成的C和O的对电势同时拟合到方解石的晶格、弹性、介电和振动实验数据，以及文石的结构和弹性性质。然后将CO32-组的势参数转移到含Mn， Fe, Mg, Ni, Zn, Co， Cd的碳酸盐矿物的结构和体积模量模型中，从而获得一套完全一致的计算碳酸盐矿物性质的相互作用参数。计算了方解石结构中掺杂二价阳离子的缺陷能，以及钙和碳酸盐离子空位的缺陷能。此外，还模拟了白云岩的各种无序类型，包括反位缺陷、堆积缺陷以及白云岩结构中Ca/Mg比增加所带来的能量。白云石排序的理论焓值为34.3 kJ/mol，与实验值吻合良好。
The electronic polarization of oxygen ions has been explicitly incorporated in a shell model to better simulate the structure of calcite and related rhombohedral carbonate minerals. Pair-potentials for Ca2+ ions and C and O comprising the carbonate molecular ion were simultaneously fitted to experimental lattice, elastic, dielectric, and vibrational data for calcite, and the structure and elastic properties of aragonite. The resulting potential parameters for the CO32- group were then transferred to models for the structures and bulk moduli of the carbonate minerals incorporating Mn, Fe, Mg, Ni, Zn, Co, Cd, and thus a fully consistent set of interaction parameters for calculating the properties of the carbonate minerals was obtained. Defect energies for doping the divalent cations into the calcite structure, and for calcium and carbonate ion vacancies were calculated. In addition, various disorder types for dolomite, including anti-site defects, stacking defects, and the energy related to increasing the Ca/Mg ratio in the dolomite structure were simulated. The theoretical enthalpy for dolomite ordering (34.3 kJ/mol) compares very well with experimental measurements.