Positronic molecule calculations using Monte Carlo configuration interaction

Coe, J. P.; Paterson, Martin J.

doi:10.1016/j.cplett.2015.12.011

Cited by 4 publications

(4 citation statements)

References 49 publications

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“…In many circumstances it was found that for small systems much of the accuracy of the FCI result could be captured using a very small fraction of the FCI space. MCCI has been extended to multipole moments, higher‐order dipole properties up to the second hyperpolarizability, X‐ray emissions and positronic molecules where, again, results could get close to that of FCI for small molecules, but used much fewer configurations. MCCI can use configuration state functions (CSFs) to guarantee that the wavefunction is always a pure spin state.…”

Section: Introductionmentioning

confidence: 99%

Open‐shell systems investigated with Monte Carlo configuration interaction

Coe

Paterson

2016

Int J of Quantum Chemistry

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We investigate the open‐shell systems of the methyl radical, the allyl radical and molecular oxygen using Monte Carlo configuration interaction. We look at whether modifying Monte Carlo configuration interaction to use the increased flexibility of unrestricted Hartree‐Fock orbitals offers any benefits in the description of these systems by the resulting compact wavefunctions. The expectation of the total spin squared when using Slater determinants is calculated to investigate if pure spin states can be evolved by Monte Carlo configuration interaction and how this might be accelerated. We consider the multireference character of these open‐shell systems. To this end we demonstrate how a previously introduced way [J. P. Coe and M. J. Paterson, J. Chem. Theory Comput. 11, 4189 (2015)] of viewing a multireference indicator of P.‐O. Löwdin [P.‐O. Löwdin, Phys. Rev. 97, 1474 (1955)] in terms of the spatial entanglement can be generalized to open‐shell systems.

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Section: Introductionmentioning

confidence: 99%

Open‐shell systems investigated with Monte Carlo configuration interaction

Coe

Paterson

2016

Int J of Quantum Chemistry

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“…Theoretical calculations have suggested that molecules can also bind Ps. Inorganic molecules such as PsOH (EA = 1.86 eV, PA = 5.43 eV 29 ), PsCN (EA = 3.86 eV, 30 PA = 5.30 eV 31 ), PsOCN (EA = 3.61 eV, 30 PA = 4.82 eV 31 ) and organic molecules such as PsCH 3 (EA = 0.08 eV, PA = 6.92 eV 32 ), HCOOPs (EA = 3.50 eV, PA = 4.78 eV 33 ), CH 3 COPs (EA = 1.58 eV, PA = 5.55 eV 33 ), meet the criterion EA[Y] + PA[Y − ] > 6.80 eV. However, to our knowledge, all research on Ps-molecule complexes has predicted PsBEs to be lower than PsBE[F].…”

Section: Introductionmentioning

confidence: 99%

Electron superhalogens as positronium superhalogens

Porras-Roldan,

Moncada,

Charry

et al. 2024

Phys. Chem. Chem. Phys.

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“…Excellent results were obtained for the H 3 molecule. Finally, other applications of MCCI include calculations of higher‐order dipole properties, X‐ray emission and absorption energies, positronic systems, and the potential energy surfaces of transition metal dimers …”

Section: Introductionmentioning

confidence: 99%

Development of spin‐orbit coupling for stochastic configuration interaction techniques

2017

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To perform spin-orbit coupling calculations on atoms and molecules, good zeroth-order wavefunctions are necessary. Here, we present the software development of the Monte Carlo Configuration Interaction (MCCI) method, to enable calculation of such properties, where MCCI iteratively constructs a multireference wavefunction using a stochastic procedure. In this initial work, we aim to establish the efficacy of this technique in predicting the splitting of otherwise degenerate energy levels on a range of atoms and small diatomic molecules. It is hoped that this work will subsequently act as a gateway toward using this method to investigate singlet-triplet interactions in larger multireference molecules. We show that MCCI can generate very good results using highly compact wavefunctions compared to other techniques, with no prior knowledge of important orbitals. Higher-order relativistic effects are neglected and spin-orbit coupling effects are incorporated using first-order degenerate perturbation theory with the Breit-Pauli Hamiltonian and effective nuclear charges in the one-electron operator. Results are obtained and presented for B, C, O, F, Si, S, and Cl atoms and OH, CN, NO, and C diatomic radicals including spin-orbit coupling constants and the relative splitting of the lowest energy degenerate state for each species. Convergence of MCCI to the full configuration interaction result is demonstrated on the multireference problem of stretched OH. We also present results from the singlet-triplet interaction between the X3Σg- and both the a1Δg and b1Σg+ states of the O molecule. © 2017 Wiley Periodicals, Inc.

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Positronic molecule calculations using Monte Carlo configuration interaction

Cited by 4 publications

References 49 publications

Open‐shell systems investigated with Monte Carlo configuration interaction

Open‐shell systems investigated with Monte Carlo configuration interaction

Electron superhalogens as positronium superhalogens

Development of spin‐orbit coupling for stochastic configuration interaction techniques

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