[QE-users] Hard PSP for copper

[Vahid Askarpour]

Dear QE Community,

I am attempting to generate a hard PSP for copper (to calculate the electrical conductivity of pure copper) by including the semi-core states as done in the atomic code manual. The semi-core states are essential for a correct evaluation of conductivity.

The spreads are:

     s(3S/3S) =  1.000000  <r> =   0.7133  <r2> =    0.5889  r(max) =   0.6112
     s(3P/3P) =  1.000000  <r> =   0.7502  <r2> =    0.6671  r(max) =   0.6189
     s(3D/3D) =  1.000000  <r> =   1.0470  <r2> =    1.5711  r(max) =   0.5961
     s(4S/4S) =  1.000000  <r> =   2.8937  <r2> =    9.8815  r(max) =   2.2428


My input file is:

&INPUT
  title='Cu',
  zed=29,
  config='[Ar] 3d10 4s1',
  rel=1,
  dft='LDA'
  iswitch=3,
  nld=3,
  rlderiv=2.41,
  eminld=-10.0,
  emaxld=4.0,
  deld=0.01,
/
&INPUTP
  pseudotype=2
  lloc=0,
 ! rcloc=1.05
  nlcc=.true.
  file_pseudopw=‘Cu.UPF',
  tm=.true.,
/
3
3P  2  1  6.00   0.00  1.25  1.25  0.0
3D  3  2 10.00  0.00  1.05  1.05  0.0
3S  1  0  2.00   0.00  1.10  1.10  0.0
&TEST
  file_pseudo=‘Cu.UPF'
  nconf=1
  configts(1)='3s2 3p6 3d10 4s1'
  ecutmin=50
  ecutmax=500
  decut=50
/

In the output, I get

     n l     nl             e AE (Ry)        e PS (Ry)    De AE-PS (Ry) 
     1 0     3S   1( 2.00)       -8.38991       -8.38991       -0.00000
     2 1     3P   1( 6.00)       -5.29424       -5.29425        0.00000
     3 2     3D   1(10.00)      -0.39133       -0.39134        0.00000
     2 0     4S   1( 1.00)       -0.35756       -0.40614        0.04858  !

The 3S, 3P and 3D match. The last one does not but the manual says it might not. 

The convergence is reached at

     Cutoff (Ry) :  200.0
                           N = 1       N = 2       N = 3
     E(L=0) =        -8.3893 Ry   -0.4061 Ry    0.0005 Ry
     E(L=1) =        -5.2513 Ry   -0.0602 Ry    0.0230 Ry
     E(L=2) =        -0.2263 Ry    0.0347 Ry    0.0793 Ry

Here 3P and 3D energies are off by 40 and 170mRy. Using P or D as reference with proper lloc does not improve the energy discrepancy.

And if I use lloc=-1 with rcloc=1.05, I get

     n l     nl             e AE (Ry)        e PS (Ry)    De AE-PS (Ry) 
     1 0     3S   1( 2.00)       -8.38991       -8.38991       -0.00000
     2 1     3P   1( 6.00)       -5.29424       -5.29425        0.00000
     3 2     3D   1(10.00)      -0.39133       -0.39134        0.00000
     2 0     4S   1( 1.00)       -0.35756       -0.35996        0.00240

4S energies look better. The convergence is reached at

     Cutoff (Ry) :  200.0
                           N = 1       N = 2       N = 3
     E(L=0) =        -8.3893 Ry   -0.3601 Ry    0.0028 Ry
     E(L=1) =        -5.2512 Ry   -0.0567 Ry    0.0232 Ry
     E(L=2) =        -0.2244 Ry    0.0347 Ry    0.0793 Ry

The 3P and 3D energies are still off by 40 and 170mRy. Changing rcloc from 0.7 to 2.0 (which is too large) does not improve the energy differences for these states.

It seems that regardless of the choice of lloc, the 3P and 3D energies remain different. 

I have checked the consistency of the derivatives and wave functions but despite the consistency, phonon calculation with convergence of even 10^-22 results in many negative frequencies not just at Gamma but at many other q-points.

Is there a trick to making the 3P and 3D energies agree beyond what I have already tried?

Thank you,

Vahid

Vahid Askarpour
Department of physics and atmospheric science
Dalhousie University
Halifax, NS