group velocity

[Saranyanarayanan]

I used (display-group-velocities) syntax for getting group velocities, which is supposed to output all of the group velocity vectors at each k-point. But I am getting group velocity vectors for the bands at the last computed k point. What am I doing wrong? How do I get group velocities at desired k-points?
when I used (output-at-kpoint (vector3 0.5 0 0) display-group-velocities) I am getting nothing in the place of group velocities.

[stevengj]

Have you tried something like (run display-group-velocities)? i.e. passing it to run so that it gets called after every k point?

[Saranyanarayanan]

Yes . I have tried that one also. Then it is showing error:
[saranya@localhost 1d2]$ mpb 1d.ctl > 1d.out
Backtrace:
12 (apply-smob/1 #<catch-closure 1147c40>)
In ice-9/eval.scm:
619:8 11 (_ #(#(#<directory (guile-user) 11e01e0>) "1d.ctl"))
619:8 10 (_ #(#(#(#<directory (guile-user) 11e01e0>) "1d.ctl") ?))
In unknown file:
9 (primitive-load "1d.ctl")
In ice-9/eval.scm:
619:8 8 (_ #(#(#<directory (guile-user) 11e01e0>) 0 #t #<vari?>))
626:19 7 (_ #(#(#<directory (guile-user) 11e01e0>) 0 #t #<vari?>))
159:9 6 (_ #(#(#<directory (guile-user) 11e01e0>) 0 #t #<vari?>))
619:8 5 (_ #(#(#(#<directory (guile-user) 11e01e0>) 0 #t #) #))
619:8 4 (_ #(#(#(#(#<directory (guile-user) 11e01e0>) 0 ?) #) #))
In ice-9/boot-9.scm:
230:17 3 (map1 (#(-0.5 0.0 0.0) #(-0.4 0.0 0.0) #(# 0.0 0.0) # ?))
230:17 2 (map1 (#<procedure display-group-velocities ()>))
In ice-9/eval.scm:
619:8 1 (_ #(#(#<directory (guile-user) 11e01e0> #<variab?> ?) ?))
330:13 0 (_ 1)

ice-9/eval.scm:330:13: ice-9/eval.scm:330:13: Wrong number of arguments to #<procedure display-group-velocities ()>
[saranya@localhost 1d2]$

[stevengj]

What does (procedure-num-args display-group-velocities) return?

[Saranyanarayanan]

I tried that one. But it's taking so much time. I started it like 4 hours ago and still it is running. I don't know why.

[stevengj]

No, what happens if you just type (procedure-num-args display-group-velocities) by itself at the mpb prompt?

[Saranyanarayanan]

It shows:
mpb> (procedure-num-args display-group-velocities)
$2 = 1