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Showing 1 to 11 of 11 for “"Natural orbitals"”.
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Development and Assessment of Pair Natural Orbitals Coupled Cluster Quadratic Response Properties
… reduced-scaling techniques, such as local pair natural orbitals (LPNOs), these advancements allow us to match experimental results and probe the fundamental behavior of complex systems. However, while significant progress has been made for ground-state energetics, such as reaction pathways and …
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A Computational Analysis of Supported and Unsupported Group 6 Transition Metal-Metal Bonds Based on the Natural Orbitals for Chemical Valence (NOCV) and the Extended Transition State (ETS) Techniques
… based on the extended transition state (ETS) and natural orbitals for chemical valence (NOCV) methods. The analysis of the unsupported triple (M2L6) and quadruple (M2L2L´2; M=Cr,Mo,W; L,L´=π-acceptor/σ-donor ligands) metal-metal bonds demonstrated that the M-M bond strength follows the trend …
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Approximate Spin Extended Hartree-Fock theory
… developed in which the Occupation Numbers of the Natural Orbitals of Charge are varied but the orbitals themselves are frozen. A number of techniques for obtaining appropriate Natural Orbitals of Charge are presented and these techniques are employed in semi-empirical and Ab-Initio studies. The …
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Towards a Reduced-Scaling Method for Calculating Coupled Cluster Response Properties
… the unsatisfactory performance of the pair natural orbital (PNO) based reduced-scaling approach for calculating linear response properties at the coupled cluster level of theory and propose novel modifications, which we refer to as PNO++, (A. Kumar and T. D. Crawford. Perturbed Pair Natural …
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DEVELOPMENT OF HIGH LEVEL AB INITIO METHODS TO DESCRIBE NONADIABATIC EVENTS AND APPLICATIONS TO THE EXCITED STATES OF SMALL BIOLOGICAL MOLECULES
… is expanded in the basis of high multiplicity natural orbitals (HMNOs). Specifically, the HMNO approach is implemented by expanding the MRCI wavefunction in the basis of natural orbitals generated from a ground state high multiplicity Configuration Interaction Singles and Doubles (CISD) …
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Quantum Monte Carlo methods for molecular systems: New developments and applications
… We have also shown that the utilization of natural orbitals leads to a significant improvement in the quality of the trial wavefunctions. We demonstrate that, through a combination of advances in both accuracy and scaling, QMC is a highly attractive alternative to the traditional methods, …
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Quantum Monte Carlo methods for molecular systems: New developments and applications
… We have also shown that the utilization of natural orbitals leads to a significant improvement in the quality of the trial wavefunctions. We demonstrate that, through a combination of advances in both accuracy and scaling, QMC is a highly attractive alternative to the traditional methods, …
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QUANTUM OBSERVABLES OF OPEN-SHELL SYSTEMS. A THEORETICAL STUDY
… the performance of the domain-based local pair natural orbital (DLPNO) variant of the “gold standard” CCSD(T) method for the prediction of phosphorescence energies of aromatic chromophores is investigated for the first time [2]. An extensive analysis of both accuracy and computational cost of …
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Quantum Embedding Methods for the Accurate Ground and Excited Electronic Structure of Large Molecular Systems
… orbital localization, utilizing intrinsic atomic orbitals. The BE matching condition is restricted to well-localized orbitals, which allows BE to converged to at least 99\% of the correlation energy in basis sets up to cc-pVDZ. For the troublesome cases involving more diffuse and polarization …
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Explicitly Correlated Methods for Large Molecular Systems
… (2016)]. The two key ideas are the use of pair-natural orbitals for compact representation of wave function amplitudes and the use of domain approximation to impose the block sparsity. This development utilizes the concepts for sparse representation of tensors described in the context of the …
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In Pursuit of Local Correlation for Reduced-Scaling Electronic Structure Methods in Molecules and Periodic Solids
… can be exploited, both in terms of the occupied orbitals and the unoccupied (or virtual) orbitals. In the case of the former, we highlight some of the historical developments in orbital localization before applying orbital localization robustly to infinite periodic crystalline systems [Clement, …