# Hydrogen diatomic molecule : computation of derivatives
# of the energy, to a very high accuracy
# Datasets 1 to 5 : GS computations at slightly different geometries,
# for finite-difference analysis of forces, including the target
# geometry (for dataset 3)
# Step 6 : RF calculation
# Note : this also tests the use of istwfk==1 in RF with
# istwfk/=1 in the GS case.
ndtset 6
xred1 -0.047 0 0 0.04690 0 0
xred2 -0.047 0 0 0.04695 0 0
xred3 -0.047 0 0 0.047 0 0
xred4 -0.047 0 0 0.04705 0 0
xred5 -0.047 0 0 0.04710 0 0
xred6 -0.047 0 0 0.047 0 0
#Specific for RF
rfphon6 1
rfatpol6 2 2
rfdir6 1 0 0
nqpt6 1
qpt6 0.0 0.0 0.0
getwfk6 3
nstep6 18
diemix6 0.35
diemac6 1.0
#Common data
acell 12 10 10
amu 1.008
diemac 1.0d0 diemix 0.5d0
ecut 4.5
getwfk -1
kptopt 0
kpt 3*0.0
natom 2
nband 1
nkpt 1
nline 3
nsym 4 ntypat 1
rprim 1 0 0 0 1 0 0 0 1
symrel 1 0 0 0 1 0 0 0 1
1 0 0 0 1 0 0 0 -1
1 0 0 0 -1 0 0 0 1
1 0 0 0 -1 0 0 0 -1
tnons 12*0
nstep 12
tolvrs 7.0d-20
typat 2*1
wtk 1
znucl 1.0
#%%
#%% [setup]
#%% executable = abinit
#%% [files]
#%% files_to_test =
#%% t33.out, tolnlines = 0, tolabs = 0.000e+00, tolrel = 0.000e+00
#%% psp_files = 1h.pspnc
#%% [paral_info]
#%% max_nprocs = 1
#%% [extra_info]
#%% keywords = NC, DFPT
#%% authors = Unknown
#%% description =
#%% H2 molecule in a big box : compute VERY accurately
#%% the derivatives of the energy, by both symmetric finite-differences and
#%% direct computation of forces and 2DTE.
#%% Also test the interplay between istwfk/=1 in the GS calculation
#%% and istwfk==1 in the RF calculation (istwfk/=1 is not yet-991020-
#%% allowed for RF, which is a shame)
#%% 1) Computation of the first-order derivative of the total energy
#%% With delta(xred)=0.0002, one gets delta(etot)/delta(xred)=-3.145846551
#%% With delta(xred)=0.0001, one gets delta(etot)/delta(xred)=-3.145836932
#%% The combination of both results, in a higher-order finite difference
#%% formula gives -3.145833726 . The direct computation of forces
#%% at the target geometry gives -3.145833725869 . The agreement is perfect,
#%% taking into account the "limited" number of digits (10) of the
#%% finite-difference result.
#%% 2) Computation of the second-order derivative of the total energy
#%% With delta(xred)=0.0002, one gets delta(dedt)/delta(xred)=188.73875
#%% With delta(xred)=0.0001, one gets delta(dedt)/delta(xred)=188.73837
#%% The combination of both results, in a higher-order finite difference
#%% formula gives 188.73824613 . The direct computation of 2DTE
#%% at the target geometry gives 188.73824613046 . The agreement at the
#%% level of 11 digits is also perfect.
#%%