Drug molecules undergo changes to their intermolecular binding patterns under extreme conditions, leading to structural phase transitions which produce different polymorphs. Polymorphism of aspirin (acetylsalicylic acid), one of the most widely consumed medications, has attracted many scientists, chemists and pharmacologists to identify its stable polymorphs and phase transformations at ambient temperatures and pressures. Here, density functional theory at the ωB97XD/6-31G* functional level is utilized to calculate the lattice constants, volumes, Gibbs free energies, vibrational spectra, stabilities and phase transitions of aspirin forms I and II at different pressures and temperatures. These computations confirm that phase transformation occurs between these two forms of aspirin at higher pressures (from 3 to 5 GPa) and near room temperatures. Taking aspirin as a case study, this work can help design, produce and store drugs, guiding scientists, chemists and pharmacologists to perform further experiments.

中文翻译：

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阿司匹林在高压和室温下的固固相变

药物分子在极端条件下会发生分子间结合模式的变化，从而导致产生不同多晶型物的结构相变。阿司匹林（乙酰水杨酸）是最广泛使用的药物之一，其多晶型现象吸引了许多科学家、化学家和药理学家来鉴定其在环境温度和压力下的稳定多晶型和相变。在这里，ωB97XD/6-31G* 功能水平的密度泛函理论用于计算阿司匹林 I 型和 II 型在不同压力和温度下的晶格常数、体积、吉布斯自由能、振动光谱、稳定性和相变。这些计算证实，这两种形式的阿司匹林在较高压力（3 到 5 GPa）和接近室温下发生相变。