scholarly journals Generalized-active-space pair-density functional theory: an efficient method to study large, strongly correlated, conjugated systems

2017 ◽  
Vol 8 (4) ◽  
pp. 2741-2750 ◽  
Author(s):  
Soumen Ghosh ◽  
Christopher J. Cramer ◽  
Donald G. Truhlar ◽  
Laura Gagliardi
Keyword(s):  
Electron Correlation ◽  
Density Functional ◽  
Organic Molecules ◽  
Open Shell ◽  
Structure Theory ◽  
Strongly Correlated ◽  
Functional Theory ◽  
Conjugated Systems ◽  
Pair Density ◽  
Accurate Treatment

Predicting ground- and excited-state properties of open-shell organic molecules by electronic structure theory can be challenging because an accurate treatment has to correctly describe both static and dynamic electron correlation.

scholarly journals Assessment of the KID Procedure on a Mo–oxo Complex, an Open–Shell System

2020 ◽  
Author(s):  
Jorge Martínez-Araya ◽  
Daniel Glossman-Mitnik
Keyword(s):  
Density Functional ◽  
Organic Molecules ◽  
Open Shell ◽  
Density Functionals ◽  
Functional Theory ◽  
Reactivity Descriptors ◽  
Shell System ◽  
Global And Local ◽  
First Time ◽  
Local Reactivity Descriptors

The KID (Koopmans in DFT) procedure usually applies in organic molecules of the closed–shell type. We used the KID procedure in an open–shell system for the first time to choose the most suitable density functional to compute global and local reactivity descriptors coming from the Conceptual Density–Functional Theory. From a set of 18 density functionals spread from the second until the fourth rung of the Jacob’s ladder: BP86, B97-D, BLYP, CAM-B3LYP, M06-L, M11-L, MN12-L, B3LYP, PBE0, N12-SX, M06-2X, M11, MN12-SX, CAM-B3LYP, LC-ωHPBE, ωB97X-D, APFD, MN15 and MN15-L, we concluded that CAM-B3LYP provides the best outcome.

scholarly journals Dipole Moment Calculations Using Multiconfiguration Pair-Density Functional Theory and Hybrid Multiconfiguration Pair-Density Functional Theory

2021 ◽  
Author(s):  
Aleksandr Lykhin ◽  
Donald Truhlar ◽  
Laura Gagliardi
Keyword(s):  
Density Functional Theory ◽  
Dipole Moment ◽  
Density Functional ◽  
Dipole Moments ◽  
Computational Cost ◽  
Strongly Correlated ◽  
Functional Theory ◽  
Active Space ◽  
Pair Density ◽  
Reasonable Behavior

The dipole moment is the molecular property that most directly indicates molecular polarity. The accuracy of computed dipole moments depends strongly on the quality of the calculated electron density, and the breakdown of single-reference methods for strongly correlated systems can lead to poor predictions of the dipole moments in those cases. Here, we derive the analytical expression for obtaining the electric dipole moment by multiconfiguration pair density functional theory (MC-PDFT), and we assess the accuracy of MC-PDFT for predicting dipole moments at equilibrium and nonequilibrium geometries. We show that MC-PDFT dipole moment curves have reasonable behavior even for stretched geometries, and they significantly improve upon the CASSCF results by capturing more electron correlation. The analysis of a dataset consisting of 18 first-row transition metal diatomics and 6 main-group polyatomic molecules with multireference character suggests that MC-PDFT and its hybrid extension (HMC-PDFT) perform comparably to CASPT2 and MRCISD+Q methods and have a mean unsigned deviation of 0.2–0.3 D with respect to the best available dipole moment reference values. We explored the dependence of the predicted dipole moments upon the choice of the on-top density functional and active space, and we recommend the tPBE and hybrid tPBE0 on-top choices for the functionals combined with the moderate correlated participating orbital scheme for selecting the active space. With these choices, the mean unsigned deviations (in debyes) of the calculated equilibrium dipole moments from the best estimates are 0.77 for CASSCF, 0.29 for MC-PDFT, 0.24 for HMC-PDFT, 0.28 for CASPT2, and 0.25 for MRCISD+Q. These results are encouraging because the computational cost of MC-PDFT or HMC-PDFT is largely reduced compared to the CASPT2 and MRCISD+Q methods.

scholarly journals Multiconfiguration Pair-Density Functional Theory

2021 ◽  
Vol 72 (1) ◽  
pp. 541-564
Author(s):  
Prachi Sharma ◽  
Jie J. Bao ◽  
Donald G. Truhlar ◽  
Laura Gagliardi
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Strongly Correlated Systems ◽  
Background Information ◽  
Total Density ◽  
Strongly Correlated ◽  
Functional Theory ◽  
Correlated Systems ◽  
Pair Density ◽  
Spin Densities

Kohn-Sham density functional theory with the available exchange–correlation functionals is less accurate for strongly correlated systems, which require a multiconfigurational description as a zero-order function, than for weakly correlated systems, and available functionals of the spin densities do not accurately predict energies for many strongly correlated systems when one uses multiconfigurational wave functions with spin symmetry. Furthermore, adding a correlation functional to a multiconfigurational reference energy can lead to double counting of electron correlation. Multiconfiguration pair-density functional theory (MC-PDFT) overcomes both obstacles, the second by calculating the quantum mechanical part of the electronic energy entirely by a functional, and the first by using a functional of the total density and the on-top pair density rather than the spin densities. This allows one to calculate the energy of strongly correlated systems efficiently with a pair-density functional and a suitable multiconfigurational reference function. This article reviews MC-PDFT and related background information.

Predicting bond dissociation energy and bond length for bimetallic diatomic molecules: a challenge for electronic structure theory

2017 ◽  
Vol 19 (8) ◽  
pp. 5839-5854 ◽  
Author(s):  
Junwei Lucas Bao ◽  
Xin Zhang ◽  
Xuefei Xu ◽  
Donald G. Truhlar
Keyword(s):  
Density Functional Theory ◽  
Active Sites ◽  
Density Functional ◽  
Electronic Structure Theory ◽  
Structure Theory ◽  
Strongly Correlated ◽  
Functional Theory ◽  
Metal Metal ◽  
Catalytically Active ◽  
Metal Bonds

We test the accuracy of Kohn–Sham density functional theory for strongly correlated metal–metal bonds that occur in catalytically active sites and intermediates and examine the orbitals and configurations involved to analyze the results.

Multiconfiguration Pair-Density Functional Theory: A New Way To Treat Strongly Correlated Systems

2016 ◽  
Vol 50 (1) ◽  
pp. 66-73 ◽  
Author(s):  
Laura Gagliardi ◽  
Donald G. Truhlar ◽  
Giovanni Li Manni ◽  
Rebecca K. Carlson ◽  
Chad E. Hoyer ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Strongly Correlated Systems ◽  
Strongly Correlated ◽  
Functional Theory ◽  
Correlated Systems ◽  
Pair Density

scholarly journals Electronic Structure Theory for X-Ray Absorption and Photoemission Spectroscopy

2021 ◽  
pp. 63-81
Author(s):  
Peter Krüger
Keyword(s):  
Electronic Structure ◽  
Electron Correlation ◽  
Density Functional ◽  
Electronic Structure Theory ◽  
Structure Theory ◽  
Photoemission Spectroscopy ◽  
Functional Theory ◽  
X Ray ◽  
Hartree Fock ◽  
X Ray Absorption

AbstractThe principles of X-ray absorption and photoemission spectroscopy calculations are introduced and the basics of electronic structure theory, including the Hartree–Fock approximation, density functional theory, its time-dependent version and quasiparticle theory are reviewed on an elementary level. Emphasis is put on polarization effects and the role played by electron correlation.

Localized Active Space Pair-Density Functional Theory

2021 ◽  
Author(s):  
Riddhish Pandharkar ◽  
Matthew R. Hermes ◽  
Christopher J. Cramer ◽  
Donald G. Truhlar ◽  
Laura Gagliardi
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Functional Theory ◽  
Active Space ◽  
Pair Density

scholarly journals Changes in CO2 Adsorption Affinity Related to Ni Doping in FeS Surfaces: A DFT-D3 Study

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 486
Author(s):  
Aleksandar Zivković ◽  
Michiel Somers ◽  
Eloi Camprubi ◽  
Helen E. King ◽  
Mariette Wolthers ◽  
...  
Keyword(s):  
Density Functional ◽  
Organic Molecules ◽  
Ni Doping ◽  
Functional Theory ◽  
Small Organic Molecules ◽  
Adsorption Affinity ◽  
The Origin Of Life ◽  
Carbon Dioxide Co2 ◽  
Partial Desorption ◽  
Good Agreement

Metal sulphides constitute cheap, naturally abundant, and environmentally friendly materials for energy storage applications and chemistry. In particular, iron (II) monosulphide (FeS, mackinawite) is a material of relevance in theories of the origin of life and for heterogenous catalytic applications in the conversion of carbon dioxide (CO2) towards small organic molecules. In natural mackinawite, Fe is often substituted by other metals, however, little is known about how such substitutions alter the chemical activity of the material. Herein, the effect of Ni doping on the structural, electronic, and catalytic properties of FeS surfaces is explored via dispersion-corrected density functional theory simulations. Substitutional Ni dopants, introduced on the Fe site, are readily incorporated into the pristine matrix of FeS, in good agreement with experimental measurements. The CO2 molecule was found to undergo deactivation and partial desorption from the doped surfaces, mainly at the Ni site when compared to undoped FeS surfaces. This behaviour is attributed to the energetically lowered d-band centre position of the doped surface, as a consequence of the increased number of paired electrons originating from the Ni dopant. The reaction and activation energies of CO2 dissociation atop the doped surfaces were found to be increased when compared to pristine surfaces, thus helping to further elucidate the role Ni could have played in the reactivity of FeS. It is expected that Ni doping in other Fe-sulphides may have a similar effect, limiting the catalytic activity of these phases when this dopant is present at their surfaces.

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