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首页> 外文期刊>Canadian Journal of Pure and Applied Sciences >STUDY OF THE STRUCTURES AND PROPERTIES OF THE MOLECULES PYRIMETHAMINE AND SULFADOXINE USING AB INITIO AND DFT METHODS
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STUDY OF THE STRUCTURES AND PROPERTIES OF THE MOLECULES PYRIMETHAMINE AND SULFADOXINE USING AB INITIO AND DFT METHODS

机译：用AB引发和DFT方法研究分子嘧啶和磺胺嘧啶的结构和性质。

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摘要

Density functional theory (DFT) and ab- initio Quantum Mechanical calculations have been used to study the structures and properties of the Molecules Pyrimethamine and Sulfadoxine. Their molecular stabilities, structures, dipole moments, charges transfer, polarizability tensors, average polarizability anisotropy, energies, IR and Raman vibrational frequencies have been predicted. Tentative assignments for their intense IR active frequencies have been carried out and represented. We have used the Restricted Hartree-Fock (RHF) and density functional Becke3LYP (B3LYP) theories by employing 6- 311++G** basis set for inclusion of electron correlation. From our results we observe that the molecules are more stable at the RHF level of theory than at the B3LYP level of theory. The frequency calculations obtained at the B3LYP level are closer to some experimental values than those obtained at the RHF level due the effect of electron correlation. The magnitude of the dipole moment is higher in the RHF level and the polarizability tensor components, the average polarizability and the anisotropy are greater at the B3LYP level. This implies that the inclusion of electron correlation decreases the dipole moment and increases the polarizability tensors, the average polarizability and the anisotropy. The IR and Raman spectra of the molecules have also been presented and the IR spectrum of Pyrimethamine lies in the same range as that given by some experimental results.
机译：密度泛函理论（DFT）和从头算起的量子力学计算已用于研究分子乙胺嘧啶和磺胺多辛的结构和性质。预测了它们的分子稳定性，结构，偶极矩，电荷转移，极化率张量，平均极化率各向异性，能量，IR和拉曼振动频率。已对其强红外活动频率进行了初步分配。我们通过使用6-311 ++ G **基集来包含电子相关性，使用了受限Hartree-Fock（RHF）和密度泛函Becke3LYP（B3LYP）理论。从我们的结果中我们观察到，分子在RHF理论水平比B3LYP理论水平更稳定。由于电子相关性的影响，在B3LYP级别获得的频率计算比在RHF级别获得的频率计算更接近一些实验值。偶极矩的大小在RHF级别较高，并且极化率张量分量，平均极化率和各向异性在B3LYP级别较大。这意味着包含电子相关性会降低偶极矩并增加极化率张量，平均极化率和各向异性。还给出了分子的红外光谱和拉曼光谱，乙胺嘧啶的红外光谱与一些实验结果在同一范围内。

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