In this study, DFT calculations were employed to assess and contrast the structural, electronic, and optical characteristics of five alanine crystal forms. The Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) with the Tkatchenko-Scheffler dispersion correction scheme was employed and compared to the PBE functional and the local density approximation (LDA) without dispersion correction. Experimentally, alanine crystal powders were characterized through X-ray diffraction (XRD) and UV-VIS absorption spectrum. Additionally, UV-VIS absorption measurements were performed on L-$\alpha$-alanine, DL-alanine, $\beta$-alanine, and alanine hydrochloride solvated in water. Significant deviations (>10%) were observed between the experimental crystal lattice parameters and those predicted by the GGA and LDA methods. Incorporating dispersion correction into the GGA functional improved prediction accuracy. Additionally, time-dependent DFT (TD-DFT) computations using the polarizable continuum model were conducted to analyze the UV/VIS absorption spectrum of $\alpha$-, $\beta$-, DL-, and hydrogen chloride alanine in water and interpret experimental data. Different alanine crystals exhibited substantial anisotropic electronic and optical properties, including effective masses, absorption, and dielectric function. The L-$\alpha$-HCl structure displayed the smallest band gap (4.67 eV), suggesting its suitability for applications such as L-$\alpha$/L-$\alpha$-HCl/L-$\alpha$ quantum well structures. The main effective masses of electrons and holes were also determined for each crystal for a better understanding of their electronic transport properties.

在本研究中，采用 DFT 计算来评估和对比五种丙氨酸晶型的结构、电子和光学特性。采用具有 Tkatchenko-Scheffler 色散校正方案的 Perdew-Burke-Ernzerhof (PBE) 广义梯度近似 (GGA)，并将其与 PBE 泛函和没有色散校正的局部密度近似 (LDA) 进行比较。实验上，通过 X 射线衍射 (XRD) 和 UV-VIS 吸收光谱对丙氨酸晶体粉末进行了表征。此外，还对 L-进行了 UV-VIS 吸收测量$\alpha$-丙氨酸、DL-丙氨酸、$\beta$-丙氨酸和丙氨酸盐酸盐溶于水。实验晶格参数与 GGA 和 LDA 方法预测的晶格参数之间观察到显着偏差 (>10%)。将色散校正纳入 GGA 函数可提高预测精度。此外，使用可偏振连续介质模型进行时间相关的 DFT (TD-DFT) 计算，以分析$\alpha$-,$\beta$-、DL-和氯化氢丙氨酸在水中并解释实验数据。不同的丙氨酸晶体表现出显着的各向异性电子和光学特性，包括有效质量、吸收和介电功能。L-$\alpha$-HCl结构显示出最小的带隙（4.67 eV），表明其适合L-等应用$\alpha$/L-$\alpha$-HCl/L-$\alpha$量子阱结构。还确定了每个晶体的电子和空穴的主要有效质量，以便更好地了解其电子传输特性。