Buelna-Garcia Carlos Emilano, Cabellos José Luis, Quiroz-Castillo Jesus Manuel, Martinez-Guajardo Gerardo, Castillo-Quevedo Cesar, de-Leon-Flores Aned, Anzueto-Sanchez Gilberto, Martin-Del-Campo-Solis Martha Fabiola
Departamento de Investigación en Polímeros y Materiales, Edificio 3G, Universidad de Sonora, Blvd. Luis Encinas y Rosales S/N, Centro, Hermosillo 83000, Mexico.
Departamento de Investigación en Fisica, Edifcio 3M, Universidad de Sonora, Blvd. Luis Encinas y Rosales S/N, Centro, Hermosillo 83000, Mexico.
Materials (Basel). 2020 Dec 29;14(1):112. doi: 10.3390/ma14010112.
The starting point to understanding cluster properties is the putative global minimum and all the nearby local energy minima; however, locating them is computationally expensive and difficult. The relative populations and spectroscopic properties that are a function of temperature can be approximately computed by employing statistical thermodynamics. Here, we investigate entropy-driven isomers distribution on BeB clusters and the effect of temperature on their infrared spectroscopy and relative populations. We identify the vibration modes possessed by the cluster that significantly contribute to the zero-point energy. A couple of steps are considered for computing the temperature-dependent relative population: First, using a genetic algorithm coupled to density functional theory, we performed an extensive and systematic exploration of the potential/free energy surface of BeB clusters to locate the putative global minimum and elucidate the low-energy structures. Second, the relative populations' temperature effects are determined by considering the thermodynamic properties and Boltzmann factors. The temperature-dependent relative populations show that the entropies and temperature are essential for determining the global minimum. We compute the temperature-dependent total infrared spectra employing the Boltzmann factor weighted sums of each isomer's infrared spectrum and find that at finite temperature, the total infrared spectrum is composed of an admixture of infrared spectra that corresponds to the spectra of the lowest-energy structure and its isomers located at higher energies. The methodology and results describe the thermal effects in the relative population and the infrared spectra.
理解团簇性质的起点是假定的全局最小值以及所有附近的局部能量最小值；然而，找到它们在计算上既昂贵又困难。可以通过运用统计热力学来近似计算作为温度函数的相对丰度和光谱性质。在此，我们研究了BeB团簇上熵驱动的异构体分布以及温度对其红外光谱和相对丰度的影响。我们确定了团簇所具有的对零点能量有显著贡献的振动模式。计算与温度相关的相对丰度考虑了几个步骤：首先，使用与密度泛函理论相结合的遗传算法，我们对BeB团簇的势能/自由能表面进行了广泛而系统的探索，以找到假定的全局最小值并阐明低能量结构。其次，通过考虑热力学性质和玻尔兹曼因子来确定相对丰度的温度效应。与温度相关的相对丰度表明，熵和温度对于确定全局最小值至关重要。我们使用每个异构体红外光谱的玻尔兹曼因子加权和来计算与温度相关的总红外光谱，发现在有限温度下，总红外光谱由对应于最低能量结构及其高能异构体光谱的红外光谱混合而成。该方法和结果描述了相对丰度和红外光谱中的热效应。
