Incremental treatments of the full configuration interaction problem

Abstract

The recent many‐body expanded full configuration interaction (MBE‐FCI) method is reviewed by critically assessing its advantages and drawbacks in the context of contemporary near‐exact electronic structure theory. Besides providing a succinct summary of the history of MBE‐FCI to date within a generalized and unified theoretical setting, its finer algorithmic details are discussed alongside our optimized computational implementation of the theory. A selected few of the most recent applications of MBE‐FCI are revisited, before we close by outlining its future research directions as well as its place among modern near‐exact wave function‐based methods. This article is categorized under: Electronic Structure Theory > Ab Initio Electronic Structure Methods

Is Externally Corrected Coupled Cluster Always Better Than the Underlying Truncated Configuration Interaction?

“…While our initial tests of the CIPSI-driven ec-CC-II and ec-CC-II 3 approaches reported in this study are very promising, encouraging us to continue our work in this direction, the present study has also pointed out that the underlying CIPSI method, especially when one adds the second-order multireference MBPT corrections to the variational energies obtained in the CIPSI Hamiltonian diagonalizations, can be made very accurate as well, being competitive with or even more accurate than the ec-CC-II 3 results. This is not a criticism of the idea of ec-CC but, rather, a recognition of the fact that the new generations of selected CI techniques, such as those developed in refs , , , , and − , the stochastic CI approaches, especially FCIQMC, − and other methods that utilize CI concepts, such as the correlation energy extrapolation by intrinsic scaling − and the incremental , and many-body expanded − FCI, along with nontraditional alternatives to FCI, such as DMRG, − have become highly competitive with the best CC solutions (cf., e.g., refs , , and − for selected recent examples; see, also, refs − for recent perspectives).…”

Active Learning Assisted MCCI to Target Spin States in Model Hamiltonian Systems

“…While computational chemistry methods have come a long way, traditional methods still find it challenging to deal with systems containing strongly correlated electrons. [1][2][3][4] Systems i such as poly-metallic complexes, conjugated polyenes and polyaromatic hydrocarbons show this phenomenon and are important for various biological, material and bio-mimetic applications. [5][6][7][8][9][10][11][12] One of the main reasons for the complication in studying such systems is the varied spin states that are possible in the low-lying energy limits for these systems.…”

Active Learning Assisted MCCI to Target Spin States

“…While computational chemistry methods have come a long way, traditional methods still find it challenging to deal with systems containing strongly correlated electrons. − Systems such as poly metallic complexes, conjugated polyenes, and polyaromatic hydrocarbons show this phenomenon and are important for various biological, material, and biomimetic applications. − One of the main reasons for the complication in studying such systems is the varied spin states that are possible in the low-lying energy limits for these systems. − While the presence of various spin states makes it difficult to understand the systems computationally, it is the same properties that can be leveraged toward energy harvesting, , catalytic activity, and in general to tune the reactivities of these systems.…”