scholarly journals Using Density Matrix Quantum Monte Carlo for Calculating Exact-on-Average Energies for ab Initio Hamiltonians in a Finite Basis Set

2020 ◽  
Vol 16 (2) ◽  
pp. 1029-1038 ◽  
Author(s):  
Hayley R. Petras ◽  
Sai Kumar Ramadugu ◽  
Fionn D. Malone ◽  
James J. Shepherd
Keyword(s):  
Monte Carlo ◽  
Density Matrix ◽  
Ab Initio ◽  
Quantum Monte Carlo ◽  
Finite Basis ◽  
Basis Set ◽  
Matrix Quantum

scholarly journals Density-matrix quantum Monte Carlo method

2014 ◽  
Vol 89 (24) ◽  
Author(s):  
N. S. Blunt ◽  
T. W. Rogers ◽  
J. S. Spencer ◽  
W. M. C. Foulkes
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Density Matrix ◽  
Quantum Monte Carlo ◽  
Quantum Monte Carlo Method ◽  
Matrix Quantum

scholarly journals Interaction picture density matrix quantum Monte Carlo

2015 ◽  
Vol 143 (4) ◽  
pp. 044116 ◽  
Author(s):  
Fionn D. Malone ◽  
N. S. Blunt ◽  
James J. Shepherd ◽  
D. K. K. Lee ◽  
J. S. Spencer ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Density Matrix ◽  
Quantum Monte Carlo ◽  
Interaction Picture ◽  
Matrix Quantum

scholarly journals The Sign Problem in Density Matrix Quantum Monte Carlo

2021 ◽  
Vol 17 (10) ◽  
pp. 6036-6052 ◽  
Author(s):  
Hayley R. Petras ◽  
William Z. Van Benschoten ◽  
Sai Kumar Ramadugu ◽  
James J. Shepherd
Keyword(s):  
Monte Carlo ◽  
Density Matrix ◽  
Quantum Monte Carlo ◽  
Sign Problem ◽  
Matrix Quantum

scholarly journals Diffusion and Reptation Quantum Monte Carlo Study of the NaK Molecule

2018 ◽  
Author(s):  
Marc E. Segovia ◽  
Oscar Ventura
Keyword(s):  
Monte Carlo ◽  
Dipole Moment ◽  
Potential Energy ◽  
Dissociation Energy ◽  
Quantum Monte Carlo ◽  
Density Functional ◽  
Basis Set ◽  
Energy Curve ◽  
Dft Methods ◽  
Trial Wavefunction

<p>Diffusion Monte Carlo (DMC) and Reptation Monte Carlo (RMC) methods, have been applied to study some properties of the NaK molecule. Hartree-Fock (HF), Density Functional (DFT) and single and double configuration interaction (SDCI) wavefunctions with a valence quadruple zeta atomic natural orbital (VQZ/ANO) basis set were used as trial wavefunctions. Values for the potential energy curve, dissociation energy and dipole moment were calculated for all methods and compared with experimental results and previous theoretical derivations. Quantum Monte Carlo (QMC) calculations were shown to be useful methods to recover correlation in NaK, essential to obtain a reasonable description of the molecule. The equilibrium distance—interpolated from the potential energy curves—yield a value of 3.5 Å, in agreement with the experimental value. The dissociation energy, however, is not as good. In this case, a conventional CCSD(T) calculation with an extended aug-pc-4 basis set gives a much better agreement to experiment. On the contrary, the CCSD(T), other MO and DFT methods are not able to reproduce correctly the large dipole moment of this molecule. Even DMC methods with a simple HF trial wavefunction are able to give a better agreement to experiment. RMC methods are even better, and the value obtained with a B3LYP trial wavefunction is very close to the experimental one.</p>

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