In a recent paper [Phys. Rev. B 90, 125150 (2014)], we showed that the random phase approximation with exchange (RPAx) gives accurate total energies for a diverse set of systems including the high and low density regime of the homogeneous electron gas, the N2 molecule, and the H2 molecule at dissociation. In this paper, we present results for the van der Waals bonded Ar2 and Kr2 dimers and demonstrate that the RPAx gives superior dispersion forces as compared to the RPA. We then show that this improved description is crucial for the bond formation of the Mg2 molecule. In addition, the RPAx performs better for the Be2 dissociation curve at large nuclear separation but, similar to the RPA, fails around equilibrium due to the build up of a large repulsion hump. For the strongly correlated LiH molecule at dissociation we have also calculated the RPAx potential and find that the correlation peak at the bond midpoint is overestimated as compared to the RPA and the exact result. The step feature is missing and hence the delocalization error is comparable to the RPA. This is further illustrated by a smooth energy versus fractional charge curve and a poor description of the LiH dipole moment at dissociation.

Molecular bonding with the RPAx: From weak dispersion forces to strong correlation / Colonna, Nicola; Hellgren, Maria Sofie; de Gironcoli, Stefano Maria. - In: PHYSICAL REVIEW. B. - ISSN 2469-9950. - 93:19(2016), pp. 1-11. [10.1103/PhysRevB.93.195108]

Molecular bonding with the RPAx: From weak dispersion forces to strong correlation

Colonna, Nicola;Hellgren, Maria Sofie;de Gironcoli, Stefano Maria
2016-01-01

Abstract

In a recent paper [Phys. Rev. B 90, 125150 (2014)], we showed that the random phase approximation with exchange (RPAx) gives accurate total energies for a diverse set of systems including the high and low density regime of the homogeneous electron gas, the N2 molecule, and the H2 molecule at dissociation. In this paper, we present results for the van der Waals bonded Ar2 and Kr2 dimers and demonstrate that the RPAx gives superior dispersion forces as compared to the RPA. We then show that this improved description is crucial for the bond formation of the Mg2 molecule. In addition, the RPAx performs better for the Be2 dissociation curve at large nuclear separation but, similar to the RPA, fails around equilibrium due to the build up of a large repulsion hump. For the strongly correlated LiH molecule at dissociation we have also calculated the RPAx potential and find that the correlation peak at the bond midpoint is overestimated as compared to the RPA and the exact result. The step feature is missing and hence the delocalization error is comparable to the RPA. This is further illustrated by a smooth energy versus fractional charge curve and a poor description of the LiH dipole moment at dissociation.
2016
93
19
1
11
195108
10.1103/PhysRevB.93.195108
https://arxiv.org/abs/1510.06914
Colonna, Nicola; Hellgren, Maria Sofie; de Gironcoli, Stefano Maria
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11767/56528
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