Knizia Gerald, Chan Garnet Kin-Lic
Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States.
J Chem Theory Comput. 2013 Mar 12;9(3):1428-32. doi: 10.1021/ct301044e. Epub 2013 Feb 21.
We extend our density matrix embedding theory (DMET) [Phys. Rev. Lett.2012, 109, 186404] from lattice models to the full chemical Hamiltonian. DMET allows the many-body embedding of arbitrary fragments of a quantum system, even when such fragments are open systems and strongly coupled to their environment (e.g., by covalent bonds). In DMET, empirical approaches to strong coupling, such as link atoms or boundary regions, are replaced by a small, rigorous quantum bath designed to reproduce the entanglement between a fragment and its environment. We describe the theory and demonstrate its feasibility in strongly correlated hydrogen ring and grid models; these are not only beyond the scope of traditional embeddings but even challenge conventional quantum chemistry methods themselves. We find that DMET correctly describes the notoriously difficult symmetric dissociation of a 4 × 3 hydrogen atom grid, even when the treated fragments are as small as single hydrogen atoms. We expect that DMET will open up new ways of treating complex strongly coupled, strongly correlated systems in terms of their individual fragments.
我们将密度矩阵嵌入理论（DMET）[《物理评论快报》，2012年，第109卷，第186404页]从晶格模型扩展到完整的化学哈密顿量。DMET允许对量子系统的任意片段进行多体嵌入，即使这些片段是开放系统且与它们的环境强烈耦合（例如，通过共价键）。在DMET中，诸如连接原子或边界区域等强耦合的经验方法被一个小的、严格的量子浴所取代，该量子浴旨在重现片段与其环境之间的纠缠。我们描述了该理论，并在强关联的氢环和网格模型中证明了其可行性；这些模型不仅超出了传统嵌入的范围，甚至对传统量子化学方法本身构成了挑战。我们发现，即使所处理的片段小至单个氢原子，DMET也能正确描述4×3氢原子网格极难的对称解离。我们期望DMET将为从各个片段的角度处理复杂的强耦合、强关联系统开辟新途径。
