Pandey Ram Dhari, de Moraes Matheus Morato F, Boguslawski Katharina, Tecmer Pawel
Institute of Physics, Faculty of Physics, Astronomy, and Informatics, Nicolaus Copernicus University in Toruń, Grudziadzka 5, 87-100 Toruń, Poland.
Department of Chemistry, University of Louisville, 2320 S. Brook St. Louisville, Kentucky 40292, United States.
J Chem Theory Comput. 2025 May 27;21(10):5049-5061. doi: 10.1021/acs.jctc.5c00057. Epub 2025 May 14.
Novel, robust, computationally efficient, and reliable theoretical methods are indispensable for the large-scale modeling of desired molecular properties. One such example is the orbital optimized pair coupled-cluster doubles (oo-pCCD) ansatz and its various CC extensions, which range from closed-shell ground- and excited-state models to open-shell variants. Specifically, the ionization-potential equation-of-motion frozen-pair (IP-EOM-fp)CC methods proved to be competitive with standard CC-type methods for modeling the ionization potentials of organic electronics. In this work, we extend the existing IP-EOM-pCCD-based methods to their double ionization potential (DIP) variants, resulting in various DIP-EOM-fpCC models, including up to double excitations. These methods open the way to reach open-shell singlet, triplet, and quintet states using various pCCD reference functions. Their accuracy is tested for the singlet-triplet gaps of the ortho-, meta-, and para-benzynes. Then, the most accurate models are applied to study the effects of boron and nitrogen doping on designing prototypical naphthalene-based donors and acceptors. Our results demonstrate consistent and reliable outcomes with standard methods and available experimental data. Most importantly, fpCC-type methods show slightly better performance than DIP-EOM-CCSD for strongly-correlated cases and similar performance for systems dominated by dynamical correlation when determining singlet-triplet gaps.
新颖、稳健、计算高效且可靠的理论方法对于大规模模拟所需分子性质而言不可或缺。一个这样的例子是轨道优化对耦合簇双激发（oo-pCCD）近似及其各种耦合簇扩展，其范围从闭壳基态和激发态模型到开壳变体。具体而言，电离势运动方程冻结对（IP-EOM-fp）耦合簇方法在模拟有机电子学的电离势方面被证明与标准耦合簇类型方法具有竞争力。在这项工作中，我们将现有的基于IP-EOM-pCCD的方法扩展到其双电离势（DIP）变体，从而产生各种DIP-EOM-fpCC模型，包括高达双激发。这些方法为使用各种pCCD参考函数达到开壳单重态、三重态和五重态开辟了道路。我们测试了它们对于邻位、间位和对位苯炔的单重态-三重态能隙的准确性。然后，将最精确的模型应用于研究硼和氮掺杂对设计原型萘基供体和受体的影响。我们的结果表明与标准方法和现有实验数据一致且可靠。最重要的是，在确定单重态-三重态能隙时，对于强相关情况，fpCC型方法表现出比DIP-EOM-CCSD稍好的性能，而对于由动态相关主导的系统则表现出相似的性能。
