Self-consistent ab initio calculations of the structural, crystallographic, electronic, optical, and physical properties as well as spontaneous polarization of P2₁ (α)-ferroelectric phase of diisopropylammonium bromide (α-DIPAB) molecular crystal are carried out. Examination of the total density of states as obtained using the generalized gradient approximation and hybrid exchange–correlation functional (HSE06) methods yields an optical bandgap of ∼ 5 eV and 6 eV, respectively. Furthermore, by using the Berry phase approach, we found that polar DIPAB exhibits a spontaneous polarization of 22.64 μC/cm², indicating that this remarkable ferroelectric molecule could be used as an alternative to replace several known ferroelectrics for piezoelectric and optoelectronic applications such as capacitors, sensors, and data storage as well as microelectromechanical system (MEMS) devices. Using the vdW + DF2 approximation, we identify the majority of the vibrational modes in the Raman spectra and analyze the modes generated by the bromine (Br) deficiency. We find that the Br deficiency strongly affects the electric and elastic properties of α-DIPAB. Furthermore, the elastic, dielectric, and piezoelectric tensors of α-DIPAB are calculated and interpreted. α-DIPAB is found to exhibit a static dielectric tensor of ∼ 2.5, i.e., slightly smaller than that of typical perovskite-based ferroelectrics. In addition, the clamped-ion piezoelectric tensor is calculated. We found that the piezoelectric coefficient e₂₁ corresponding to applying uniaxial strain in the direction perpendicular to the N–C bonds is smaller than the e₂₂ principle coefficient. Moreover, the components e₁₅ = 0.220 C/m² and e₃₅ = −0.2032 C/m² correspond to applying shear strain η₃₁, indicating a reasonable piezoelectric response of this polar crystal and making it a cheap attractive candidate for piezoelectric applications. The components of the elastic moduli tensor are calculated and interpreted. The α-DIPAB exhibits Young’s modulus of up to 50 GPa along specific crystalline directions despite its relatively low hardness. We attribute such a large value to the presence of a dense H–Br bond network between the Br and DIPAB molecule. The Poisson ratio is also strongly anisotropic, with values ranging from 0.5 to 0.2. The DIPAB systems are brittle based on the ratio between the bulk and shear elastic constants, suggesting that this material has potential for use in flexible electronic applications. A real-part dielectric anomaly at T = 140 K induced by iodine doping of α-DIPAB exhibits switchable behavior. This abnormality can be attributed to suppression of ferroelectricity induced by trapping of vortices at dislocation defects generated by iodine. Another dielectric anomaly found in the vicinity of the Curie temperature of α-DIPAB can be explained in terms of a structural phase-induced ferroelectric-to-paraelectric transition.

进行结构，晶体学，电子，光学和物理性质以及溴化二异丙基铵铵（α-DIPAB）分子的P2 ₁（α）-铁电相的自发极化的自洽从头计算。使用广义梯度逼近和混合交换-相关函数（HSE06）方法对状态总密度进行检查，得出的光学带隙分别约为5 eV和6 eV。此外，通过使用贝里相位的方法，我们发现，极性DIPAB展品22.64自发极化 μ C /厘米²，表明这种卓越的铁电分子可以替代压电和光电应用中的几种已知铁电体，例如电容器，传感器，数据存储以及微机电系统（MEMS）器件。使用vdW + DF2逼近，我们确定了拉曼光谱中的大多数振动模式，并分析了由溴（Br）缺乏产生的模式。我们发现，Br缺乏会严重影响α-DIPAB的电和弹性。此外，计算并解释了α-DIPAB的弹性，介电和压电张量。发现α-DIPAB的静态介电张量约为2.5，即比典型的基于钙钛矿的铁电体的介电张量稍小。此外，计算出钳位离子压电张量。我们发现压电系数与垂直于N-C键的方向施加单轴应变相对应的e ₂₁小于e _22主系数。此外，这些组件È ₁₅  = 0.220 C /米²和Ë ₃₅  = -0.2032 C /米²对应于施加剪切应变η ₃₁，表明该极性晶体的合理压电响应，使其成为压电应用的廉价诱人候选物。计算和解释弹性模量张量的分量。尽管其相对较低的硬度，但α-DIPAB沿特定的结晶方向仍具有高达50 GPa的杨氏模量。我们将这么大的价值归因于Br和DIPAB分子之间存在致密的H-Br键网络。泊松比也具有很强的各向异性，值范围从0.5到0.2。基于体积弹性常数和剪切弹性常数之间的比率，DIPAB系统是脆性的，这表明该材料具有在柔性电子应用中使用的潜力。T处的实部介电异常 α-DIPAB的碘掺杂引起的= 140 K表现出可切换的行为。该异常可归因于抑制由碘产生的位错缺陷处的涡流捕获而引起的铁电。在α-DIPAB居里温度附近发现的另一个介电异常可以用结构相诱导的铁电-顺电转变来解释。