Cook Cameron, McKinley Jessica L, Beran Gregory J O
Department of Chemistry, University of California, Riverside, California 92521, USA.
J Chem Phys. 2021 Apr 7;154(13):134109. doi: 10.1063/5.0044385.
The ability to predict not only what organic crystal structures might occur but also the thermodynamic conditions under which they are the most stable would be extremely useful for discovering and designing new organic materials. The present study takes a step in that direction by predicting the temperature- and pressure-dependent phase boundary between the α and β polymorphs of resorcinol using density functional theory (DFT) and the quasi-harmonic approximation. To circumvent the major computational bottleneck associated with computing a well-converged phonon density of states via the supercell approach, a recently developed approximation is employed, which combines a supercell phonon density of states from dispersion-corrected third-order density functional tight binding [DFTB3-D3(BJ)] with frequency corrections derived from a smaller B86bPBE-XDM functional DFT phonon calculation on the crystallographic unit cell. This mixed DFT/DFTB quasi-harmonic approach predicts the lattice constants and unit cell volumes to within 1%-2% at lower pressures. It predicts the thermodynamic phase boundary in almost perfect agreement with the experiment, although this excellent agreement does reflect fortuitous cancellation of errors between the enthalpy and entropy of transition.
不仅能够预测可能出现的有机晶体结构，还能预测它们最稳定时的热力学条件，这对于发现和设计新型有机材料将极为有用。本研究朝着这个方向迈出了一步，通过使用密度泛函理论（DFT）和准谐近似来预测间苯二酚α和β多晶型物之间随温度和压力变化的相界。为了规避通过超胞方法计算收敛良好的声子态密度所带来的主要计算瓶颈，采用了一种最近开发的近似方法，该方法将色散校正的三阶密度泛函紧束缚[DFTB3-D3(BJ)]的超胞声子态密度与基于晶体学单胞上较小的B86bPBE-XDM泛函DFT声子计算得出的频率校正相结合。这种混合DFT/DFTB准谐方法在较低压力下预测晶格常数和晶胞体积的误差在1%-2%以内。它预测的热力学相界与实验结果几乎完全一致，尽管这种极好的一致性确实反映了转变焓和熵之间误差的偶然抵消。
