Correction to Embedded Mean-Field Theory

J. Chem. Theory Comput.

et al. 2019

123

We present a quantum embedding method that allows for the calculation of local excited states embedded in a Kohn-Sham density functional theory (DFT) environment. Projection-based quantum embedding methodologies provide a rigorous framework for performing DFT-in-DFT and wave function in DFT (WF-in-DFT) calculations. The use of absolute localization, where the density of each subsystem is expanded in only the basis functions associated with the atoms of that subsystem, provide improved computationally efficiency for WF-in-DFT calculations by reducing the number of orbitals in the WF calculation. In this work, we extend absolutely localized projection-based quantum embedding to study localized excited states using EOM-CCSD-in-DFT and TDDFT-in-DFT. The embedding results are highly accurate compared to the corresponding canonical EOM-CCSD and TDDFT results on the full system, with TDDFT-in-DFT frequently more accurate than canonical TDDFT. The 1 arXiv:1909.12423v1 [physics.chem-ph] 26 Sep 2019 absolute localization method is shown to eliminate the spurious low-lying excitation energies for charge transfer states and prevent over delocalization of excited states.Additionally, we attempt to recover the environment response caused by the electronic excitations in the high-level subsystem using different schemes and compare their accuracy. Finally, we apply this method to the calculation of the excited state energy of green fluorescent protein and show that we systematically converge to the full system results. Here we demonstrate how this method can be useful in understanding excited states, specifically which chemical moieties polarize to the excitation. This work shows absolutely localized projection-based quantum embedding can treat local electronic excitations accurately, and make computationally expensive WF methods applicable to systems beyond current computational limits. many systems. 16 However, the computational cost of EOM-CCSD (scaling as O(N 6 )) restricts its usage to about 50 or fewer atoms in a moderate basis. Methods that extend the applicability of EOM-CCSD to larger systems include the use of local orbitals, [17][18][19][20][21] restricted virtual spaces, 22,23 and multiscale approaches. [24][25][26][27] Multiscale approaches treat different regions of the molecule with methods of varying cost and accuracy to reflect their importance. 28,29 For example, one may use EOM-CCSD to describe the important region of the molecule while using molecular mechanics (MM), in EOM-CCSD-in-MM methods, [30][31][32] or DFT, in EOM-CCSD-in-DFT methods, 33 to describe the remainder of the molecule. Such approaches take advantage of the high accuracy of EOM-CCSD and the low scaling of MM or DFT to go beyond the size/accuracy limits of any one method alone.Density functional theory embedding provides a formally exact framework for performing multiscale calculations. This approach has been shown to be accurate for combining density functional theory with wave function theory. The key choice in density function theory embedd...

Section: Resultsmentioning

confidence: 99%

“…The Manby and Miller groups proposed the use of the parameter-dependent levelshift projection operator (hereinafter the µ operator) as 45,[60][61][62][63][64]…”

Section: Absolute Localization Projection-based Embeddingmentioning

confidence: 99%

Absolutely Localized Projection-Based Embedding for Excited States

J. Chem. Theory Comput.

et al. 2019

123

“…18 Quantum embedding calculations seek to improve upon the small model simulations by including some influence of the full system on the final energy. Quantum embedding methods such as QM/MM, 19 ONIOM, 20 DMET, 21,22 embedded mean-field theory, [23][24][25][26][27] Green's function embedding, 22,[28][29][30] partition DFT, [31][32][33] and DFT embedding 22,[34][35][36][37] among many others [38][39][40][41][42][43] were designed to combine the benefits of high accuracy and systematic improvability from WF theory for a small subsystem, while including effects from the full system at a comparably negligible computational cost. Projection operator based DFT embedding has been developed by many groups with significant success.…”

Section: Introductionmentioning

confidence: 99%

Huzinaga Projection Embedding for Efficient and Accurate Energies of Systems with Localized Spin-densities

et al. 2021

Preprint

We demonstrate the accuracy and efficiency of the restricted open-shell and unrestricted formulation of the absolutely localized Huzinaga projection operator embedding method. Restricted open-shell and unrestricted Huzinaga projection embedding in the full system basis is formally exact to restricted open-shell and unrestricted Kohn-Sham density functional theory, respectively. By utilizing the absolutely localized basis, we significantly improve the efficiency of the method, while maintaining high accuracy. The open-shell embedding method is shown to calculate electronic energies of a variety of systems to within 1 kcal/mol accuracy of the full system wave function result. For certain highly localized reactions, such as spin transition energies on transition metals, we find that very few atoms are necessary to include in the wave function region, in order to achieve desired accuracy. Here we apply our method to several representative examples such as spin splitting energies, catalysis on transition metals, and radical reactions.

“…Frequently, one is interested in chemical transformations that are localized to a small region of the overall system, such as bond formation or elimination, molecular adsorption, or bond rotation. Many embedding methods, such as QM/MM, ONIOM, DMET, , embedded mean-field theory, − Green’s function embedding, ,, partition DFT, − and DFT embedding , among many others, − take advantage of this intrinsic localization of chemical transformations to achieve substantially improved accuracy for a nominal additional computational cost. By dividing the total system into subsystems, important local interactions can be accurately modeled at a significantly reduced computational cost.…”

Section: Introductionmentioning

confidence: 99%

Robust, Accurate, and Efficient: Quantum Embedding Using the Huzinaga Level-Shift Projection Operator for Complex Systems

J. Chem. Theory Comput.

et al. 2020

Wave function (WF) in density functional theory (DFT) embedding methods provide a framework for performing localized, high accuracy WF calculations on a system, while not incurring the full computational cost of the WF calculation on the full system. In order to effectively partition a system into localized WF and DFT subsystems, we utilize the Huzinaga level-shift projection operator within an absolutely localized basis. In this work, we study the ability of the absolutely localized Huzinaga level-shift projection operator method to study complex WF and DFT partitions, including partitions between multiple covalent bonds, a double bond, and transition metal-ligand bonds. We find that our methodology can accurately describe all of these complex partitions. Additionally, we study the robustness of this method with respect to the 1 arXiv:1911.12449v1 [physics.chem-ph] 27 Nov 2019 WF method, specifically where the embedded systems were described using a multiconfigurational WF method. We found that the method is systematically improvable with respect to both the number of atoms in the WF region and the size of the basis set used, with energy errors less than 1 kcal/mol. Additionally, we calculated the adsorption energy of H 2 to a model of an iron metal organic framework to within 1 kcal/mol compared to CASPT2 calculations performed on the full model while incurring only a small fraction of the full computational cost. This work demonstrates that the absolutely localized Huzinaga level-shift projection operator method is applicable to very complex systems with difficult electronic structures.