Relaxations diverge near minimum for systems with 30+ atoms
Posted: Fri Jan 04, 2019 7:32 pm
Hello,
I am working on relaxing some structures for phonon calculations. The first few iterations of the relaxations work as expected (energies and forces decreasing with each step), but eventually, rather the converging, the structures tend to explode and the energy skyrockets.
Has anyone experienced this, and are there any straightforward solutions?
I have used the same input file for smaller structures (5 atom unit cells, for example) with no problems, but when the number of atoms increases above some point, the relaxations don't seem to want to converge.
Here's a copy of an input file which is yielding these results:
Thanks!
-Ali
I am working on relaxing some structures for phonon calculations. The first few iterations of the relaxations work as expected (energies and forces decreasing with each step), but eventually, rather the converging, the structures tend to explode and the energy skyrockets.
Has anyone experienced this, and are there any straightforward solutions?
I have used the same input file for smaller structures (5 atom unit cells, for example) with no problems, but when the number of atoms increases above some point, the relaxations don't seem to want to converge.
Here's a copy of an input file which is yielding these results:
Code: Select all
#Definition of lattice parameters
#********************************
acell 7.25654831700000E+00 7.25654831700000E+00 59.85153084
#Definition atomic positions and types
#*************************************
autoparal 1
#paral_kgb 0
ntypat 4
znucl 8 56 38 22 # O Ba Sr Ti, resp.
natom 40
typat 24*1 4*2 4*3 8*4 # 3*O Ba Sr Ti
xred
5.00087541357545E-01 2.14633372526376E-04 -7.46735128155745E-05
2.14633372526376E-04 5.00087541357545E-01 -7.46735128155745E-05
5.00044688983175E-01 5.00044688983175E-01 5.97952522743837E-02
5.00001094706433E-01 5.60322961643697E-06 1.21088837578999E-01
5.60322961643697E-06 5.00001094706433E-01 1.21088837578999E-01
5.00003502477752E-01 5.00003502477752E-01 1.81600304538899E-01
5.00001036610509E-01 2.08086542004534E-06 2.42559566159457E-01
2.08086542004535E-06 5.00001036610509E-01 2.42559566159457E-01
5.00008483670634E-01 5.00008483670634E-01 3.03189020862497E-01
5.00008328829892E-01 2.36348719240361E-05 3.64084796363000E-01
2.36348719240361E-05 5.00008328829892E-01 3.64084796363000E-01
5.00234577444169E-01 5.00234577444169E-01 4.25831842182860E-01
5.02028496658046E-01 1.75209586724716E-03 4.88191423057621E-01
1.75209586724716E-03 5.02028496658046E-01 4.88191423057621E-01
5.01960150800529E-01 5.01960150800529E-01 5.52026463192058E-01
5.02005928702603E-01 1.99825077359706E-03 6.14382582111844E-01
1.99825077359706E-03 5.02005928702603E-01 6.14382582111844E-01
5.01999941169098E-01 5.01999941169098E-01 6.77906382313048E-01
5.02004779481058E-01 2.00136138187207E-03 7.42465038343483E-01
2.00136138187207E-03 5.02004779481058E-01 7.42465038343483E-01
5.01998620005522E-01 5.01998620005522E-01 8.06187575503565E-01
5.01989837689835E-01 1.98638778704002E-03 8.70983026748717E-01
1.98638778704002E-03 5.01989837689835E-01 8.70983026748717E-01
5.01790857522287E-01 5.01790857522287E-01 9.34475754314373E-01
1.98944981369487E-03 1.98944981369487E-03 5.53811128671388E-01
1.99937484749006E-03 1.99937484749006E-03 6.79835713342948E-01
1.99918039454326E-03 1.99918039454326E-03 8.08171706180889E-01
1.69335827236728E-03 1.69335827236728E-03 9.36855390347336E-01
6.34313393378159E-06 6.34313393378159E-06 6.15582751578484E-02
1.01232587480401E-06 1.01232587480401E-06 1.83136477703920E-01
1.02177293817475E-06 1.02177293817475E-06 3.04609788500644E-01
1.48818204568999E-04 1.48818204568999E-04 4.26347043404420E-01
5.00215546313640E-01 5.00215546313640E-01 1.31142261565501E-03
4.99999083606990E-01 4.99999083606990E-01 1.23125207245481E-01
4.99999860659742E-01 4.99999860659742E-01 2.44668194477996E-01
4.99998427084385E-01 4.99998427084385E-01 3.66725611926493E-01
5.01851231279732E-01 5.01851231279732E-01 4.91244546601817E-01
5.01987712530747E-01 5.01987712530747E-01 6.17187644881765E-01
5.01988404968349E-01 5.01988404968349E-01 7.45319646562142E-01
5.01969261541422E-01 5.01969261541422E-01 8.73712315146007E-01
#Parameters1 of1 the SCF cycles
#****************************
iscf 7
nstep 200
#Plane wave basis and k-point grid
#*********************************
ecut 50
ecutsm 0.5
ngkpt 10 10 1
nshiftk 1
shiftk 0 0 0.5
ndtset 2 jdtset 1 6
#DATASET1 : scf calculation: GS WF in the BZ
#********************************************
prtden1 1
kptopt1 1
toldfe1 1.0d-12
#DATASET6 : Ionic relaxation
optcell6 0
ionmov6 2
toldff6 2.0d-7
getxred6 -1
getcell6 -1
ntime6 200
dilatmx6 1.05
tolmxf6 2.0d-6
Thanks!
-Ali