CCSD(T) 对于极具挑战性的C5H2异构体的旋转常数 - - 理论与实验之间的比较
Venkatesan S Thimmakondu1, Amir Karton2
1Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA 92182-1030, USA.
Molecules (Basel, Switzerland)
|September 28, 2023
概括
对于具有挑战性的C5H2异构体来说,准确计算平衡旋转常数是困难的,即使使用合集群方法. 双混合DFT函数对这些复杂分子表现最好.
科学领域:
- 计算化学计算化学
- 量子化学 是一个量子化学.
- 频谱学是一种光谱学.
背景情况:
- 精确确定分子结构和性质在化学中至关重要.
- 旋转常数是基本的光谱参数,为分子几何提供了洞察力.
- 对像C5H2这样的复杂,低的同位素来说,计算这些常数带来了重大的理论挑战.
研究的目的:
- 评估结合集群 (CCSD(T)) 和各种密度函数理论 (DFT) 方法的准确性,用于计算四种C5H2同体的平衡旋转常数 (Ae,Be,Ce).
- 将计算结果与从实验数据中得出的半实验旋转常数进行比较.
- 为这些具有挑战性的系统评估Jacob's Ladder中DFT函数的性能.
主要方法:
- 高级ab initio合集群计算 (CCSD(T)) 使用不同的基础集 (冷核心和全电子).
- 应用一系列密度函数理论 (DFT) 方法,包括纯函数,混合函数和双混合函数.
- 通过减去振动贡献,将振动平均的实验旋转常数 (A0,B0,C0) 转换为平衡值 (Ae,Be,Ce).
主要成果:
- 结合的集群计算揭示了准确预测所有C5H2异构体的平衡旋转常数的重大挑战,某些常数的误差高达3%.
- 纯粹的DFT函数 (BLYP-D3BJ,PBE-D3BJ,TPSS-D3BJ) 的性能优于全局和范围分离的混合函数.
- 双混合式DSD-PBEP86-D3BJ方法显示了最佳的整体性能,在大多数情况下,错误率低于0.5%.
结论:
- 对于具有复杂电子结构的C5H2异构体来说,计算精确的平衡旋转常数是很苛刻的,即使对于CCSD也是如此.
- DFT方法,特别是双混合函数,为这些系统提供了更高的计算效率和更准确的替代方案.
- 这些发现为选择适当的理论方法提供了有价值的指导,用于对具有挑战性的分子物种进行光谱性质预测.
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