Thermodynamics of the Flexible Metal-Organic Framework Material MIL-53(Cr) From First Principles.
Thermodynamics of the Flexible Metal-Organic Framework Material MIL-53(Cr) From First Principles.
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DOI：
10.1021/acs.jpcc.6b11692
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发表时间：
2017-03
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影响因子：
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通讯作者：
Cockayne E
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作者：
Cockayne E
我们使用第一性原理密度泛函理论总能量和线性响应声子计算的Helmholtz和Gibbs自由能作为温度，压力和细胞体积的函数在柔性金属有机骨架材料MIL-53（铬）的准谐波近似。进行GGA和MetaGGA计算，每个计算包括在D2、D3或D3（BJ）参数化下的经验货车范德华力（vdW）。在温度高达500 K和压力从-30 MPa到30 MPa的所有温度下，发现自由能与体积的关系有两个极小值，对应于窄孔（np）和大孔（lp）结构。确定了临界正压力和临界负压力，超过该压力，只有一个自由能最小值。虽然所有结果都高估了np相相对于lp相的稳定性，但对于具有D3或D3（BJ）vdW力的metaGGA PBESol+RTPSS+U+J方法，发现与实验的最佳总体一致性。对于这些参数化，计算的np-lp跃迁的自由能垒仅为3至6 kJ每摩尔的Cr 4（OH）4（C8 H4 O 4）4。
We use first-principles density functional theory total energy and linear response phonon calculations to compute the Helmholtz and Gibbs free energy as a function of temperature, pressure, and cell volume in the flexible metal-organic framework material MIL-53(Cr) within the quasiharmonic approximation. GGA and metaGGA calculations were performed, each including empirical van der Waals (vdW) forces under the D2, D3, or D3(BJ) parameterizations. At all temperatures up to 500 K and pressures from −30 MPa to 30 MPa, two minima in the free energy versus volume are found, corresponding to the narrow pore (np) and large pore (lp) structures. Critical positive and negative pressures are identified, beyond which there is only one free energy minimum. While all results overestimated the stability of the np phase relative to the lp phase, the best overall agreement with experiment is found for the metaGGA PBEsol+RTPSS+U+J approach with D3 or D3(BJ) vdW forces. For these parameterizations, the calculated free energy barrier for the np-lp transition is only 3 to 6 kJ per mole of Cr4(OH)4(C8H4O4)4.