Categories
notebook

Doping Si NCs with Li and Na

Workplan

  • (done) Partir da bulk-superlattice e dopar com Na e Li nos sites T e O
  • (done) Criar base da densidade de carga tipo 2 para o Na e Li

A supercelula do bulk está em:
blafis:/home/coutinho/research/f4-tcnq/fcc-si317/bulk/res.fcc-si317h172

  • (done) Calculate Na$^{(0/+)}$ and Li$^{(0/+)}$ in a Si-NC in a box to understand the effect of the superlattice
  • Produce figures with levels of Li, Na and TCNQ without charge correction;
  • Calculate migration barrier of Li$^{(0)}$ and Na$^{(0)}$ in the NC core (9 NEB images);
  • Calculate absorption barrier of Li$^{(0)}$ and Na$^{(0)}$ into the NC (9 NEB images);
  • Calculate migration barrier of Li$^{(+)}$ and Na$^{(+)}$ in the NC core (9 NEB images);
  • Calculate absorption barrier of Li$^{(+)}$ and Na$^{(+)}$ into the NC (9 NEB images);

Basis

parameter{ecut=200}
species{pot=11-Na-9, wfbas=atom-pppp, cdbas=atom-2-5xs, normalize}
species{pot=3-Li-3,  wfbas=atom-pppp, cdbas=atom-2-5xs, normalize}

Energies and Levels

==============================================================================================================================
str            E(0)            E(+)            E_rel       E(0)-E(+)   E(-)-E(0)   E(0)-E*(+)  E*(-)-E(0)
               [Hr]            [Hr]            [eV]        [eV]        [eV]        [eV]        [eV]
------------------------------------------------------------------------------------------------------------------------------
fcc-bulk      -1353.86075     -1353.92476                  1.74180     3.60905     1.61979     3.73106
------------------------------------------------------------------------------------------------------------------------------
Na - fcc
   Th         -1401.44947     -1401.58313      0.02503     3.63707                 3.51506
   Oh         -1401.42752     -1401.56457      0.62232     3.72932                 3.60731
   [111]      -1401.45039     -1401.58465      0.00000     3.65340                 3.53139
   c-Th       -1401.39612     -1401.52659      1.47676     3.55027                 3.42826
------------------------------------------------------------------------------------------------------------------------------
Li - fcc
   Th         -1361.17023     -1361.29105      0.50178     3.28768                 3.16567
   Oh         -1361.14869     -1361.26373      1.08791     3.13040                 3.00839
   [111]      -1361.16714     -1361.29867      0.58586     3.57911                 3.45710
   c-Th       -1361.18867     -1361.31927      0.00000     3.55381                 3.43180
==============================================================================================================================
fcc-bulk   E(-)=-1353.72812 Hr

Starred values include a Madelung correction (see F4-TCNQ molecules in Si-NC superlattices).

Increasing superlattice parameter

==============================================================================================================================
str            E(0)            E(+)            E_rel       E(0)-E(+)   E(-)-E(0)   E(0)-E*(+)  E*(-)-E(0)
               [Hr]            [Hr]            [eV]        [eV]        [eV]        [eV]        [eV]
------------------------------------------------------------------------------------------------------------------------------
fcc80-bulk    -1353.67707     -1353.60655                 -1.91895     0.14585    -2.09223     0.31914
------------------------------------------------------------------------------------------------------------------------------
Na - fcc80
   Th         -1401.23826     -1401.24548      0.85770     0.19647                 0.02319
   Oh         -1401.23834     -1401.24591      0.85553     0.20599                 0.03271
   [111]      -1401.26978     -1401.27374      0.00000     0.10776                -0.06552
   c-Th       -1401.21868     -1401.21753      1.39050    −0.03129                -0.20457
------------------------------------------------------------------------------------------------------------------------------
Li - fcc80
   Th         -1360.95887     -1360.92842      1.22179    −0.82859                -1.00187
   Oh         -1360.95934     -1360.92641      1.20900    −0.89607                -1.06935
   [111]      -1360.97748     -1360.97515      0.71539    −0.06340                -0.23668
   c-Th       -1361.00377     -1361.00300      0.00000    −0.02095                -0.19423
==============================================================================================================================
fcc80-bulk E(-)=-1353.67171

As F4-TCNQ molecules in Si-NC superlattices, we applied a Madelung correction (starred values), using the following parameters. The super-lattice constant is now $a_0=4.2334~~\text{nm}$ (80.00 a.u.) and the nanocrystal’s volume is maintained, so the new estimation for the macroscopic dielectric constant is $\epsilon_{SL}=4.50$. For a fcc lattice we have $E_M(q=1)=0.17328~\text{eV}$.
No structural relaxation was performed in these cases.

Results from the previous tables are pictured below.

SVG not supported

Levels (0/+) of Na (black) and Li (orange) with Madelung corrections for several structures (solid lines) and the effect of increasing superlattice constant (dashed lines).

Ion diffusion

Absorption barriers

A work in progress …
SVG not supported

Migration barriers

A work in progress …
SVG not supported
SVG not supported