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Dear all Abinit users,

I am doing the calculation of lifetime of positron in a system.

Firstly, I did the calculation for the bulk crystal, of which the results was reasonable:


2 computations of positron lifetime have been performed (with different enhancement factors).
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Results for electron-positron annihilation:

2 computations of positron lifetime have been performed (with different enhancement factors).
########## Lifetime computation 1

# Zero-positron density limit of Arponen and Pajanne provided by Boronski & Nieminen
Ref.: Boronski and R.M. Nieminen, Phys. Rev. B 34, 3820 (1986)
# Enhancement factor of Boronski & Nieminen
Ref.: Boronski and R.M. Nieminen, Phys. Rev. B 34, 3820 (1986)

Positron lifetime (ps) = 1.76982865E+02
Positron lifetime with IPM for core elec. (ps) = 1.77968006E+02
Annihilation rate (ns-1) = 5.65026449E+00
Annihilation rate with IPM for core elec. (ns-1) = 5.61898749E+00

Annihilation rate core/valence decomposition:
Core contribution to ann.rate (ns-1) = 1.92284941E-01
Valence contribution to ann.rate (ns-1) = 5.45797955E+00
Core contribution to ann.rate with IPM (ns-1) = 1.52738915E-01
Valence contribution to ann.rate with IPM (ns-1) = 5.46624857E+00

Annihilation rate PAW decomposition:
Plane-wave contribution to ann.rate (ns-1) = 5.50569463E+00
Plane-wave valence contribution to ann.rate (ns-1) = 5.40031681E+00
On-site core contribution to ann.rate (ns-1) = 8.69071200E-02
On-site valence contribution to ann.rate (ns-1) = 5.76627416E-02
Plane-wave contribution to ann.rate with IPM (ns-1) = 5.46338637E+00
Plane-wave core contrb. to ann.rate with IPM (ns-1) = 4.92529228E-02

########## Lifetime computation 2

# Zero-positron density limit of Arponen and Pajanne provided by Boronski & Nieminen
Ref.: Boronski and R.M. Nieminen, Phys. Rev. B 34, 3820 (1986)
# Enhancement factor of Boronski & Nieminen IN THE RPA LIMIT
Ref.: Boronski and R.M. Nieminen, Phys. Rev. B 34, 3820 (1986)

Positron lifetime (ps) = 1.71787038E+02
Positron lifetime with IPM for core elec. (ps) = 1.72714978E+02
Annihilation rate (ns-1) = 5.82116096E+00
Annihilation rate with IPM for core elec. (ns-1) = 5.78988582E+00

Annihilation rate core/valence decomposition:
Core contribution to ann.rate (ns-1) = 1.92312014E-01
Valence contribution to ann.rate (ns-1) = 5.62884894E+00
Core contribution to ann.rate with IPM (ns-1) = 1.52738915E-01
Valence contribution to ann.rate with IPM (ns-1) = 5.63714690E+00

Annihilation rate PAW decomposition:
Plane-wave contribution to ann.rate (ns-1) = 5.67660667E+00
Plane-wave valence contribution to ann.rate (ns-1) = 5.57119068E+00
On-site core contribution to ann.rate (ns-1) = 8.68960201E-02
On-site valence contribution to ann.rate (ns-1) = 5.76582647E-02
Plane-wave contribution to ann.rate with IPM (ns-1) = 5.63439865E+00
Plane-wave core contrb. to ann.rate with IPM (ns-1) = 4.92529228E-02

(*) IPM=Independent particle Model

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However, I got non-reasonable results for layered system cut from the bulk crystal, I got very large lifetime (~10^4) and NAN, as shown below:
--------------------------------------------------------------------------------
Results for electron-positron annihilation:

2 computations of positron lifetime have been performed (with different enhancement factors).

########## Lifetime computation 1

# Zero-positron density limit of Arponen and Pajanne provided by Boronski & Nieminen
Ref.: Boronski and R.M. Nieminen, Phys. Rev. B 34, 3820 (1986)
# Enhancement factor of Boronski & Nieminen
Ref.: Boronski and R.M. Nieminen, Phys. Rev. B 34, 3820 (1986)

Positron lifetime (ps) = 2.07153012E+04
Positron lifetime with IPM for core elec. (ps) = 1.83846983E+04
Annihilation rate (ns-1) = 4.82734955E-02
Annihilation rate with IPM for core elec. (ns-1) = 5.43930600E-02

Annihilation rate core/valence decomposition:
Core contribution to ann.rate (ns-1) = -6.70884690E-03
Valence contribution to ann.rate (ns-1) = 5.49823424E-02
Core contribution to ann.rate with IPM (ns-1) = 1.46405028E-04
Valence contribution to ann.rate with IPM (ns-1) = 5.42466550E-02

Annihilation rate PAW decomposition:
Plane-wave contribution to ann.rate (ns-1) = 4.80691215E-02
Plane-wave valence contribution to ann.rate (ns-1) = 5.49410335E-02
On-site core contribution to ann.rate (ns-1) = 1.63065086E-04
On-site valence contribution to ann.rate (ns-1) = 4.13088913E-05
Plane-wave contribution to ann.rate with IPM (ns-1) = 5.42085500E-02
Plane-wave core contrb. to ann.rate with IPM (ns-1) = 4.48253595E-06
########## Lifetime computation 2

# Zero-positron density limit of Arponen and Pajanne provided by Boronski & Nieminen
Ref.: Boronski and R.M. Nieminen, Phys. Rev. B 34, 3820 (1986)
# Enhancement factor of Boronski & Nieminen IN THE RPA LIMIT
Ref.: Boronski and R.M. Nieminen, Phys. Rev. B 34, 3820 (1986)

Positron lifetime (ps) = NaN
Positron lifetime with IPM for core elec. (ps) = 1.52801976E+04
Annihilation rate (ns-1) = NaN
Annihilation rate with IPM for core elec. (ns-1) = 6.54441797E-02

Annihilation rate core/valence decomposition:
Core contribution to ann.rate (ns-1) = NaN
Valence contribution to ann.rate (ns-1) = NaN
Core contribution to ann.rate with IPM (ns-1) = 1.46405028E-04
Valence contribution to ann.rate with IPM (ns-1) = 6.52977746E-02

Annihilation rate PAW decomposition:
Plane-wave contribution to ann.rate (ns-1) = NaN
Plane-wave valence contribution to ann.rate (ns-1) = NaN
On-site core contribution to ann.rate (ns-1) = 1.63065083E-04
On-site valence contribution to ann.rate (ns-1) = 4.13088249E-05
Plane-wave contribution to ann.rate with IPM (ns-1) = 6.52596698E-02
Plane-wave core contrb. to ann.rate with IPM (ns-1) = 4.48253595E-06

(*) IPM=Independent particle Model

================================================================================

The calculations were done with pbe_paw pseudo-potentials from the library of abinit. The ecut and pawecutdg were set 12. and 24., respectively, with 12 12 12 k-mesh for bulk calculation and 12 1 12 for layered calculation.

Could anyone please tell me if there is something that I overlooked when calculating the lifetime of layered material.

Best regards
Zhishuo Huang

Dear Zhishuo Huang,

I suppose you had a look at : Phys. Rev. B 92, 125113.
In this paper several details are given about PAW datasets to be used for positron calculations.
In the case of defect, it is strongly recommended to use specific PAW datasets using semicore states (to be built by yourself using the ATOMPAW generator).

Regards

Dear Torrent,

Thank you so much for the recommendation. I will try to generate PAW datasets including semi-core state.
I will inform you what is going on.

Best regards
Zhishuo Huang

torrent wrote:Dear Zhishuo Huang,

I suppose you had a look at : Phys. Rev. B 92, 125113.
In this paper several details are given about PAW datasets to be used for positron calculations.
In the case of defect, it is strongly recommended to use specific PAW datasets using semicore states (to be built by yourself using the ATOMPAW generator).

Regards