Wong Bryan M, Piacenza Manuel, Della Sala Fabio
Materials Chemistry Department, Sandia National Laboratories, Livermore, California 94551, USA.
Phys Chem Chem Phys. 2009 Jun 14;11(22):4498-508. doi: 10.1039/b901743g. Epub 2009 Apr 24.
The absorption and fluorescence properties in a class of oligothiophene push-pull biomarkers are investigated with a long-range-corrected (LC) density functional method. Using linear-response time-dependent density functional theory (TDDFT), we calculate excitation energies, fluorescence energies, oscillator strengths, and excited-state dipole moments. To benchmark and assess the quality of the LC-TDDFT formalism, an extensive comparison is made between LC-BLYP excitation energies and approximate coupled cluster singles and doubles (CC2) calculations. When using a properly-optimized value of the range parameter, mu, we find that the LC technique provides an accurate description of charge-transfer excitations as a function of biomarker size and chemical functionalization. In contrast, we find that re-optimizing the fraction of Hartree Fock exchange in conventional hybrid functionals still yields an inconsistent description of excitation energies and oscillator strengths for the two lowest excited states in our series of biomarkers. The results of the present study emphasize the importance of a distance-dependent contribution of exchange in TDDFT for investigating excited-state properties.
采用长程校正（LC）密度泛函方法研究了一类寡聚噻吩推拉型生物标志物的吸收和荧光特性。利用线性响应含时密度泛函理论（TDDFT），我们计算了激发能、荧光能、振子强度和激发态偶极矩。为了对LC-TDDFT形式体系的质量进行基准测试和评估，我们对LC-BLYP激发能与近似耦合簇单双激发（CC2）计算结果进行了广泛比较。当使用范围参数μ的适当优化值时，我们发现LC技术能够准确描述电荷转移激发随生物标志物大小和化学官能化的变化。相比之下，我们发现重新优化传统杂化泛函中哈特里-福克交换的比例，对于我们系列生物标志物中两个最低激发态的激发能和振子强度，仍然给出不一致的描述。本研究结果强调了在TDDFT中，交换的距离依赖贡献对于研究激发态性质的重要性。
