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improve the performance and accuracy #159

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Dec 3, 2024
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improve the performance and accuracy #159

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59 changes: 42 additions & 17 deletions src/sigma_OHE.f90
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Original file line number Diff line number Diff line change
Expand Up @@ -271,7 +271,8 @@ subroutine sigma_ohe_calc_symm(mu_array, KBT_array, BTau_array, Nband_Fermi_Leve

!> we get the kpath by Btau_final=-exponent_max*BTauMax, but we only use half of them
!> means that we can reach the accuracy as to exp(-exponent_max)
exponent_max= 30
! exponent_max= 30
exponent_max= 15

!> exclude all kpoints with zero velocity x B and large energy away from Fermi level
do iband= 1, Nband_Fermi_Level
Expand Down Expand Up @@ -964,13 +965,17 @@ subroutine cal_sigma_iband_k
BTau= BTau_array(ibtau)

if (NBTau==1)then
NSlice_Btau_local= 2
! NSlice_Btau_local= 2
NSlice_Btau_local= 1
else
NSlice_Btau_local= (ibtau-1)*NSlice_Btau_inuse/(NBTau-1)/2
! NSlice_Btau_local= (ibtau-1)*NSlice_Btau_inuse/(NBTau-1)/2
NSlice_Btau_local= (ibtau-1)*NSlice_Btau_inuse/(NBTau-1)
if (NSlice_Btau_local==0)then
NSlice_Btau_local= 2
! NSlice_Btau_local= 2
NSlice_Btau_local= 1
else
DeltaBtau= exponent_max/2d0/NSlice_Btau_local
! DeltaBtau= exponent_max/2d0/NSlice_Btau_local
DeltaBtau= exponent_max/NSlice_Btau_local
endif
endif

Expand All @@ -980,21 +985,41 @@ subroutine cal_sigma_iband_k
!> The core of Chamber formular is to get the average of velocity
!> in the relaxation time approximation
v_k= klist_iband(iband)%velocity_k(:, 1+ishift)
if (BTau>eps3.and.NSlice_Btau_local>2) then
! set weight
do it=1, NSlice_Btau_local
weights(it) = exp(-DeltaBtau*(it-1d0))
enddo
!> trapezoidal integral
! if (BTau>eps3.and.NSlice_Btau_local>2) then
if (BTau>eps3.and.NSlice_Btau_local>1) then
velocity_bar_k= 0d0
do it=1, NSlice_Btau_local
!> five point integration(n=4)
do it=1, NSlice_Btau_local, 4 !(hj, j=it-1, j mod 4==0, Aj=28/45)
velocity_bar_k= velocity_bar_k+ &
DeltaBtau*exp(-(it-1d0)*DeltaBtau)*klist_iband(iband)%velocity_k(:, it+ishift)
28.0d0/45.0d0*DeltaBtau*exp(-(it-1d0)*DeltaBtau)*klist_iband(iband)%velocity_k(:, it+ishift)
enddo
do it=2, NSlice_Btau_local, 4 !(hj, j=it-1, j mod 4==1, Aj=64/45)
velocity_bar_k= velocity_bar_k+ &
64.0d0/45.0d0*DeltaBtau*exp(-(it-1d0)*DeltaBtau)*klist_iband(iband)%velocity_k(:, it+ishift)
enddo
velocity_bar_k= velocity_bar_k &
- 0.5d0*DeltaBtau*(exp(-(NSlice_Btau_local-1d0)*DeltaBtau)&
* klist_iband(iband)%velocity_k(:, NSlice_Btau_local+ishift) &
+ klist_iband(iband)%velocity_k(:, 1+ishift))
do it=3, NSlice_Btau_local, 4 !(hj, j=it-1, j mod 4==2, Aj=24/45)
velocity_bar_k= velocity_bar_k+ &
24.0d0/45.0d0*DeltaBtau*exp(-(it-1d0)*DeltaBtau)*klist_iband(iband)%velocity_k(:, it+ishift)
enddo
do it=4, NSlice_Btau_local, 4 !(hj, j=it-1, j mod 4==3, Aj=64/45)
velocity_bar_k= velocity_bar_k+ &
64.0d0/45.0d0*DeltaBtau*exp(-(it-1d0)*DeltaBtau)*klist_iband(iband)%velocity_k(:, it+ishift)
enddo
velocity_bar_k= velocity_bar_k-14.0d0/45.0d0*DeltaBtau*klist_iband(iband)%velocity_k(:, 1+ishift)
! set weight
! do it=1, NSlice_Btau_local
! weights(it) = exp(-DeltaBtau*(it-1d0))
! enddo
! !> trapezoidal integral
! velocity_bar_k= 0d0
! do it=1, NSlice_Btau_local
! velocity_bar_k= velocity_bar_k+ &
! DeltaBtau*exp(-(it-1d0)*DeltaBtau)*klist_iband(iband)%velocity_k(:, it+ishift)
! enddo
! velocity_bar_k= velocity_bar_k &
! - 0.5d0*DeltaBtau*(exp(-(NSlice_Btau_local-1d0)*DeltaBtau)&
! * klist_iband(iband)%velocity_k(:, NSlice_Btau_local+ishift) &
! + klist_iband(iband)%velocity_k(:, 1+ishift))

!> Simpson's integral
!> add the first and the last term
Expand Down
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