Dear Bogdan,
I gave several tries, but none of them looks okay. The first thing I noticed is the total energy started to converge after I changed pseudopotentials from PAW to LDA or GGA as suggested in the older post PAW+DFPT+GGA has unreasonable energy values - #5 by baguetl. I chose occopt = 4 instead of occopt = 3 (Fermi-Dirac for metal) because occopt = 4 seems to be more reasonable than occopt = 3 for the bulk results:
Bulk with occopt = 3 (strange)
xred
V 0 0 0.5
Te 1/3 2/3 0.245
Te 2/3 1/3 0.755
Bulk with occopt = 4 (reasonable)
xred
V 0 0 0.5
Te 1/3 2/3 0.245
Te 2/3 1/3 0.755
Hence, I used occopt = 4 for the following tests:
Try1-3 of monolayer VTe2: Pseudopotential = LDA/ occopt = 4
xred (optcell = 0)
V 0 0 0.5/4
Te 1/3 2/3 0.2396/4
Te 2/3 1/3 0.7604/4
VTe2_1_1_try2.abi (4.4 KB)
VTe2_1_1_try2.log (2.0 MB)
xred (Te is farther away from V)
V 0 0 0.5/4
Te 1/3 2/3 0.2326/4
Te 2/3 1/3 0.7674/4
xred (Te is closer to V, bulk’s xred)
V 0 0 0.5/4
Te 1/3 2/3 0.245/4
Te 2/3 1/3 0.755/4
Try4 of monolayer VTe2: Pseudopotential = GGA/ occopt = 4
xred (optcell = 0)
V 0 0 0.5/4
Te 1/3 2/3 0.2396/4
Te 2/3 1/3 0.7604/4
VTe2_1_1.abi (4.4 KB)
VTe2_1_1.log (2.1 MB)
All results show negative frequencies for a broad range of k-space. Do you have other suggestions for getting a better result?
Thank you!
Best regards,
WH Peng