The control of thermal expansion represents a challenge in materials design. This work shows that the length of the lattice parameter is a key element for controlling thermal expansion. By varying the lattice parameter through external pressure, chemical or other methods, the single-well potential energy of the polyhedra rotations (or of the atomic transverse vibrations) responsible for negative thermal expansion (NTE), can be turned into a quartic anharmonic potential or into a double-well potential, thus enhancing or suppressing the NTE, respectively. This result applied to framework materials should be taken into account to overcome the challenge of controlling thermal expansion.

中文翻译：

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关于框架材料的正负热膨胀之间的转换

热膨胀的控制代表了材料设计中的挑战。这项工作表明，晶格参数的长度是控制热膨胀的关键因素。通过外部压力，化学或其他方法改变晶格参数，可将负负热膨胀（NTE）的多面体旋转（或原子横向振动）的单阱势能转换为四次非谐能或进入双阱势，从而分别增强或抑制NTE。应该考虑将该结果应用于框架材料，以克服控制热膨胀的挑战。