A multireference coupled-cluster method for ground and excited states calculations of interstellar molecules

亚利桑那大学的Ludwik Adamowicz教授得到了化学系化学理论、模型和计算方法项目的奖励。他的项目是基于使用量子力学(QM)的基本原理来预测原始分子系统的化学和物理性质。其中一些分子，例如最简单的三原子离子H3+，在我们的宇宙演化中发挥了关键作用。Adamowicz教授的QM计算将使用当今最强大的计算机来提供与实验天体化学/天体物理研究相关的分子的光谱转变和化学行为的结果。这项研究的主要工作将是开发新的QM计算方法，其精度与目前的实验测量精度相匹配，甚至超过目前的实验测量精度。我们对天文世界的大部分知识来自于原子和分子对电磁辐射的吸收、发射和散射。对原子和分子光谱的天文观测，包括跃迁能量、强度和光偏振，补充了实验室实验和Adamowicz小组的新理论计算，以更好地了解恒星大气及其演化。Adamowicz教授将邀请理科和非理科本科生应用现代计算方法。他使这个项目中开发的新软件可供更广泛的科学界使用。Adamowicz教授和他的团队正在开发利用第一原理量子力学来研究气相中小分子系统的化学和物理性质的新方法。这些方法有望将计算量子化学的预测能力提高到目前方法无法达到的精度水平。第一个重点是活动空间多参考耦合团簇方法，该方法可以应用于研究处于平衡结构和远离平衡结构的分子的基态和激发态。第二个重点是开发使用全电子显式关联高斯波函数进行分子计算的方法。基于Born-Oppenheimer(BO)近似的方法和非BO方法也在发展中。在转动计算中实现了ECG。Adamowicz教授和他的团队正在应用新的方法研究各种分子体系的性质和光谱，如HCO+、CH5+、H3+、HeH2+、HeH、LiHe+、BEH+、LiH2+等。这些都对宇宙的星际化学从原始阶段到现在都很重要。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Professor Ludwik Adamowicz of the University of Arizona is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry. His project is based on using fundamental principles of quantum mechanics (QM) in predicting chemical and physical properties of primordial molecular systems. Some of these molecules, for example, the simplest triatomic ion H3+, has played a pivotal role in the evolution of our universe. Professor Adamowicz's QM calculations will use the most powerful present-day computers to provide results pertaining to the spectral transitions and chemical behavior of molecules relevant to experimental astrochemical/astrophysical research. The major effort in this research will go to the development of new QM computational methods whose accuracy matches or even exceeds the accuracy of present-day experimental measurements. Most of our knowledge of the astronomical world is derived from the absorption, emission and scattering of electromagnetic radiation from atoms and molecules. Astronomical observations of atomic and molecular spectra, including transition energies, intensities, and light polarization, complement both laboratory experiments and the new theoretical calculations from the Adamowicz group to develop a better understanding of stellar atmospheres and their evolutions. Professor Adamowicz will engage both science and non-science undergraduate students in the application of modern computational methods. He makes the new software developed in this project available to the broader scientific community.Professor Adamowicz and his group are developing new methods that utilize first-principles quantum mechanics to study chemical and physical properties of small and medium-size molecular systems in the gas phase. The methods are expected to elevate the predictive capability of computational quantum chemistry to a level of accuracy unattainable using present-day approaches. The first focus is on an active-space multireference coupled-cluster method that can be applied to study molecules in their ground and excited states at and away from their equilibrium structures. The second focus is on developing methods for performing molecular calculations with all-electron explicitly correlated Gaussian (ECG) functions. Methods based on the Born-Oppenheimer (BO) approximation and non-BO methods are also being developed. The ECGs are implemented in rovibrational calculations. Professor Adamowicz and his group are applying the new methods to study properties and spectra of various molecular systems such as HCO+, CH5+, H3+, HeH2+, HeH, LiHe+, BeH+, LiH2+, etc.. These are all important to the interstellar chemistry of the universe from its primordial stages to the present.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.