scholarly journals Analytic Gradients for Complete Active Space Pair-Density Functional Theory

2017 ◽  
Vol 14 (1) ◽  
pp. 126-138 ◽  
Author(s):  
Andrew M. Sand ◽  
Chad E. Hoyer ◽  
Kamal Sharkas ◽  
Katherine M. Kidder ◽  
Roland Lindh ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Functional Theory ◽  
Complete Active Space ◽  
Active Space ◽  
Pair Density

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 Separated-pair approximation and separated-pair pair-density functional theory

2016 ◽  
Vol 7 (3) ◽  
pp. 2399-2413 ◽  
Author(s):  
Samuel O. Odoh ◽  
Giovanni Li Manni ◽  
Rebecca K. Carlson ◽  
Donald G. Truhlar ◽  
Laura Gagliardi
Keyword(s):  
Density Functional Theory ◽  
Wave Function ◽  
Density Functional ◽  
Function Theory ◽  
Pair Approximation ◽  
Functional Theory ◽  
Complete Active Space ◽  
Pair Density ◽  
Comparable Accuracy ◽  
The Cost

Here we present the separated-pair approximation for wave function theory and show that it performs almost as well as the more demanding complete active space approximation. We show that the combination of an SP wave function with an on-top density functional yields comparable accuracy to CASPT2 at a small fraction of the cost.

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.

Active Space Dependence in Multiconfiguration Pair-Density Functional Theory

2018 ◽  
Vol 14 (2) ◽  
pp. 660-669 ◽  
Author(s):  
Prachi Sharma ◽  
Donald G. Truhlar ◽  
Laura Gagliardi
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Functional Theory ◽  
Active Space ◽  
Pair Density ◽  
Space Dependence
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