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Keep the full complex generalized group velocity in kappa_offdiag #185

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Merged
mjv500 merged 1 commit into from
Aug 17, 2026
Merged

Keep the full complex generalized group velocity in kappa_offdiag #185

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18 changes: 12 additions & 6 deletions src/thermal_conductivity/kappa.f90
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Original file line number Diff line number Diff line change
Expand Up @@ -95,7 +95,7 @@ subroutine get_kappa_offdiag(dr, qp, uc, fc, temperature, classical, mem, mw, ka
real(r8), dimension(3, 3), intent(out) :: kappa_offdiag

!> The off diagonal group velocity
real(r8), dimension(:, :, :), allocatable :: buf_vel
complex(r8), dimension(:, :, :), allocatable :: buf_vel
!> The off diagonal group velocity, squared
real(r8), dimension(:, :, :, :), allocatable :: buf_velsq
!> The qpoint
Expand All @@ -116,7 +116,7 @@ subroutine get_kappa_offdiag(dr, qp, uc, fc, temperature, classical, mem, mw, ka
complex(r8), dimension(:, :, :), allocatable :: buf_grad_dynmat
complex(r8), dimension(:, :), allocatable :: kronegv, buf_egv, buf_egw, buf_cm0, buf_cm1, buf_cm2
complex(r8), dimension(3) :: cv0
real(r8), dimension(3) :: v0, v1
complex(r8), dimension(3) :: v0, v1
integer :: a1, a2, ia, ib, ic, ix, iy, iz, k, iop, i, ii, j, jj

! Some buffers
Expand Down Expand Up @@ -207,9 +207,12 @@ subroutine get_kappa_offdiag(dr, qp, uc, fc, temperature, classical, mem, mw, ka
cv0 = buf_cm2(ii, :)
! remove tiny numbers.
cv0 = lo_chop(cv0, 1E-10/(lo_groupvel_Hartreebohr_to_ms/1000))
! I can take the real part since at the end we sum over
! both modes and the imaginary components disappear.
buf_vel(:, i, j) = real(cv0, r8)
! Keep the full complex velocity. The imaginary parts do cancel
! in sum_ij v_ij, but the quantity accumulated below is quadratic
! and sum_ij Im v^a Im v^b does not vanish. Discarding it makes
! kappa_offdiag depend on the arbitrary phases of the eigenvectors
! returned by zheev.
buf_vel(:, i, j) = cv0
end do
end do

Expand All @@ -226,7 +229,10 @@ subroutine get_kappa_offdiag(dr, qp, uc, fc, temperature, classical, mem, mw, ka
do k = 1, qp%ip(iq)%n_full_point
iop = qp%ip(iq)%operation_full_point(k)
v1 = matmul(uc%sym%op(abs(iop))%m, v0)
buf_velsq(:, :, i, j) = buf_velsq(:, :, i, j) + lo_outerproduct(v1, v1)
! lo_outerproduct conjugates its first argument, so the real part
! here is Re v^a Re v^b + Im v^a Im v^b, the gauge invariant form.
buf_velsq(:, :, i, j) = buf_velsq(:, :, i, j) + &
real(lo_outerproduct(v1, v1), r8)
end do
end do
end do
Expand Down
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