对于单电子性质的基于 pCCD 的预期值方法
Rahul Chakraborty1, Somayeh Ahmadkhani1, Julian Świerczyński1
1Institute of Physics, Faculty of Physics, Astronomy, and Informatics, Nicolaus Copernicus University in Toruń, Grudziadzka 5, Toruń 87-100, Poland.
The journal of physical chemistry. A
|July 16, 2025
概括
预期值合集群理论 (XCC) 通过对合集群双重 (pCCD) 方法有效计算分子特性. 局部化的pCCD轨道对于确定有机分子中的单电子性质是有效的.
科学领域:
- 量子化学是一种量子化学.
- 计算化学是一种计算化学.
- 分子建模分子建模
背景情况:
- 预期值合集群理论 (XCC) 为分子性质评估提供了一个计算效率高的路线.
- 在成本效益高的合集群 (CC) 模型中应用XCC,如对合集群双重 (pCCD) 和其扩展仍然未被充分探索.
研究的目的:
- 在XCC框架内实施和研究一个电子的低密度矩阵.
- 为了评估与pCCD结合的XCC,冷对结合集群 (fpCC) 和冷对线性结合集群 (fpLCC) 的性能,用于分子性质计算.
主要方法:
- 从集群振幅直接开发出基于预期值的密度矩阵,绕过计算密集的兰巴达方程解决方案.
- 采用pCCD,fpCC和fpLCC变体来计算一个电子的低密度矩阵.
- 计算了各种分子的双极和四极时刻.
主要成果:
- 基于预期值的密度矩阵为响应CC密度提供了一个计算上更便宜的替代方案.
- 基于pCCD的XCC方法,特别是在局部的pCCD轨道上,对单电子性质具有很好的准确性.
- 使用哈特里-福克规范轨道和优化的pCCD轨道对CCSD的基准测试验证了这些发现.
结论:
- 实现的基于预期值的密度矩阵方法在计算上具有优势.
- 建议使用基于pCCD的XCC方法进行局部化的pCCD轨道来准确和高效地计算有机分子中的单电子特性.
相关概念视频
01:27π Electron Effects on Chemical Shift: Overview
1.1K
An applied magnetic field causes loosely bound π-electrons in organic molecules to circulate, producing a local or induced diamagnetic field over a large spatial volume. As the molecules tumble in solution, the field generated by π-electrons in spherical substituents results in a zero net field. However, the net field generated by π-electrons in non-spherical substituents is not zero. The effect of this induced field depends on the orientation of the molecule with respect to B0,...
1.1K
01:20¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
1.2K
When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
1.2K
01:29Atomic Emission Spectroscopy: Lab
249
AES is a powerful analytical technique, especially effective when used with plasma sources, producing abundant spectra in characteristic emission lines. The Inductively Coupled Plasma (ICP), in particular, yields superior quantitative analytical data due to its high stability, low noise, low background, and minimal interferences under optimal experimental conditions. However, newer air-operated microwave sources are emerging as promising alternatives that could be more cost-effective than...
249
02:28Electronic Structure of Atoms
24.5K
An atom comprises protons and neutrons, which are contained inside the dense, central core called the nucleus, with electrons present around the nucleus. Taking into account the wave–particle duality of electrons and the uncertainty in position around the nucleus, quantum mechanics provides a more accurate model for the atomic structure. It describes atomic orbitals as the regions around the nucleus where electrons of discrete energy exist, characterized by four quantum...
24.5K
03:02Standard Electrode Potentials
45.0K
On comparing the reactivity of silver and lead, it is observed that the two ionic species, Ag+ (aq) and Pb2+ (aq), show a difference in their redox reactivity towards copper: the silver ion undergoes spontaneous reduction, while the lead ion does not. This relative redox activity can be easily quantified in electrochemical cells by a property called cell potential. This property is commonly known as cell voltage in electrochemistry, and it is a measure of the energy which accompanies the charge...
45.0K
01:14π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds
1.3K
In aromatic compounds, such as benzene, the circulation of (4n + 2) π-electrons sets up a diamagnetic or diatropic ring current around the perimeter of the molecule. This current induces a magnetic field that opposes the external field inside the ring and reinforces it on the outside. The protons in benzene are deshielded and exhibit high chemical shifts in the range 6.5–8.5 ppm. The shielding effect at the center of the ring is evident in complex aromatic molecules, such as...
1.3K