Schautz Friedemann, Buda Francesco, Filippi Claudia
Instituut-Lorentz, Universiteit Leiden, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands.
J Chem Phys. 2004 Sep 22;121(12):5836-44. doi: 10.1063/1.1777212.
Despite significant advances in electronic structure methods for the treatment of excited states, attaining an accurate description of the photoinduced processes in photoactive biomolecules is proving very difficult. For the prototypical photosensitive molecules, formaldimine, formaldehyde, and a minimal protonated Schiff base model of the retinal chromophore, we investigate the performance of various approaches generally considered promising for the computation of excited potential energy surfaces. We show that quantum Monte Carlo can accurately estimate the excitation energies of the studied systems if one constructs carefully the trial wave function, including in most cases the reoptimization of its determinantal part within quantum Monte Carlo. While time-dependent density functional theory and quantum Monte Carlo are generally in reasonable agreement, they yield a qualitatively different description of the isomerization of the Schiff base model. Finally, we find that the restricted open shell Kohn-Sham method is at variance with quantum Monte Carlo in estimating the lowest-singlet excited state potential energy surface for low-symmetry molecular structures.
尽管在用于处理激发态的电子结构方法方面取得了重大进展，但事实证明，要准确描述光活性生物分子中的光诱导过程非常困难。对于典型的光敏分子，即亚甲亚胺、甲醛以及视网膜发色团的最小质子化席夫碱模型，我们研究了各种通常被认为有望用于计算激发态势能面的方法的性能。我们表明，如果仔细构建试探波函数，包括在大多数情况下在量子蒙特卡罗方法中对其行列式部分进行重新优化，量子蒙特卡罗方法可以准确估计所研究体系的激发能。虽然含时密度泛函理论和量子蒙特卡罗方法总体上有合理的一致性，但它们对席夫碱模型异构化的描述在性质上有所不同。最后，我们发现，对于低对称分子结构，受限开壳层科恩-沙姆方法在估计最低单重激发态势能面时与量子蒙特卡罗方法不一致。
