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Accurate ab initio determination of the adiabatic potential energy function and the Born–Oppenheimer breakdown corrections for the electronic ground state of LiH isotopologues
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10.1063/1.3555758
/content/aip/journal/jcp/134/9/10.1063/1.3555758
http://aip.metastore.ingenta.com/content/aip/journal/jcp/134/9/10.1063/1.3555758

Figures

Image of FIG. 1.
FIG. 1.

Convergence of the vibrational levels of 7LiH calculated using different electron correlation methods with respect to the full-CI results. See Sec. II for details of the ab initio calculations.

Image of FIG. 2.
FIG. 2.

Relative differences of 7LiH potential energy curves (hartree), scaled to the dissociation energy limit, calculated with the MR-CISD+QP method and different cc-pwCVXZ (X = Q,5,6) basis sets with respect to the highest level 6Z/(56) PEC. See Sec. II for details of the ab initio calculations.

Image of FIG. 3.
FIG. 3.

Convergence of the vibrational levels of 7LiH calculated for potential energy curves obtained with the MR-CISD+QP method and different cc-pwCVXZ (X = Q,5,6) basis sets with respect to the highest level 6Z/(56) results. Upper panel: calculations with conventional basis sets. Lower panel: “noncorrelated” part of the energy obtained with the cc-pwCV6Z basis. See Sec. II for details of the ab initio calculations.

Image of FIG. 4.
FIG. 4.

Comparison of the calculated vibrational levels of 7LiH with the experimental determinations (Ref. 19). The figure also shows the importance of the different contributions [DBOC, relativistic effect, nonadiabatic contribution (β)] and the use of atomic versus nuclear masses. See text for more explanations.

Image of FIG. 5.
FIG. 5.

Comparison of the ab initio and empirical DBOC functions. The ab initio function has been obtained with the MR-CISD method using a 8-3-1 reference space and the cc-pwCVTZ basis. The empirical function is plotted using the parameters of Ref. 19. Curves are shifted to zero energy value near the equilibrium bond length (3 bohr).

Image of FIG. 6.
FIG. 6.

Comparison of the ab initio and empirical atomic DBOC functions. The ab initio function has been obtained with the MR-CISD method using a 8-3-1 reference space and the cc-pwCVTZ basis. The empirical functions are plotted using the parameters of Ref. 19. Curves are shifted to zero energy value near the equilibrium bond length (3 bohr).

Image of FIG. 7.
FIG. 7.

Perturbative mass–velocity-Darwin relativistic correction to the ground electronic state potential energy curve of LiH calculated with the internally contracted MR-CISD method using different cc-pwCVXZ (X = T,Q,5) basis sets.

Image of FIG. 8.
FIG. 8.

MR-CISD adiabatic potential energy curves of the eight lowest electronic states of LiH calculated using the cc-pwCV5Z basis set and a 4 electrons in 15 orbitals (8-3-1) CAS reference wave function.

Image of FIG. 9.
FIG. 9.

MR-CISD nonadiabatic couplings of the ground 1Σ+0) state with three excited 1Σ+1, ψ4, ψ7) electronic states of 7LiH calculated using the cc-pwCV5Z basis set and a 4 electrons in 16 orbitals (8-3-1) CAS reference wave function.

Image of FIG. 10.
FIG. 10.

Dependence of the BO breakdown correction β(R) of 7LiH on the number of nonadiabatic coupling terms n used in the summation of Eq. (3).

Image of FIG. 11.
FIG. 11.

Mass dependence of BO breakdown correction β(R) for studied isotopologues 7LiH, 6LiH, 7LiD, and 6LiD.

Tables

Generic image for table
Table I.

Vibrational energies (with respect to ZPE), dissociation energy (cm−1), and equilibrium bond length (bohr) of 7LiH calculated from potential energy curves obtained by different correlated methods and the cc-pwCVQZ basis set. See Sec. II for details of the ab initio calculations.

Generic image for table
Table II.

Vibrational energies (with respect to ZPE), dissociation energy (cm−1), and equilibrium bond length (bohr) of 7LiH calculated for potential energy curves obtained with the MR-CISD+QP method and different cc-pwCVXZ (X = Q,5,6) basis sets [the abbreviation XZ (X = Q,5,6) is used for simplicity] with/without extrapolation to CBS included [the abbreviation (XY) (X,Y = Q,5,6) is used where X and Y denote cardinal numbers of basis sets used in the extrapolation]. See Sec. II for details of the ab initio calculations and extrapolations.

Generic image for table
Table III.

Contribution of the DBOC to the vibrational levels and dissociation energy (cm−1) of 7LiH obtained with the MR-CISD+QP method using different basis sets and different reference CAS spaces. See Sec. II for details of the ab initio calculations.

Generic image for table
Table IV.

Contributions (in cm−1) to the vibrational energy levels using nuclear masses. All data refer to the most abundant isotopologue (7LiH).

Generic image for table
Table V.

Comparison of ab initio and empirical vibrational levels (in cm−1) for different isotopologues of LiH. Nuclear masses and the BO breakdown correction β(R) have been used in the vibrational levels calculations.

Generic image for table
Table VI.

Comparison of ab initio and empirical vibrational levels (in cm−1) for different isotopologues of LiH. Atomic masses have been used in the vibrational level calculations.

Generic image for table
Table VII.

Summary of rms deviations between ab initio and empirical values of vibrational energies.

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/content/aip/journal/jcp/134/9/10.1063/1.3555758
2011-03-03
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Accurate ab initio determination of the adiabatic potential energy function and the Born–Oppenheimer breakdown corrections for the electronic ground state of LiH isotopologues
http://aip.metastore.ingenta.com/content/aip/journal/jcp/134/9/10.1063/1.3555758
10.1063/1.3555758
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