Dear Quantum Espresso,
I am trying to run a test simulation on the silicon unit cell using vc-relax. When I run the simulation using "ibrav=2" the simulation converges in 4 scf cycles. However, when I attempt to run the simulation using "ibrav = 0" it doesn't converge in 18 scf cycles. Moreover, I always receive the error that I need to use a larger cell factor. Finally, and when using a larger cell factor, the simulation runs longer and doesn't converge and also gives me the same error again. I am using this test because I will need to run vc-relax in a situation where I will need to use "ibrav=0" so it is important to me that I get it to work properly. I have attached my input file below. Any clarifications on this issue would be greatly appreciated. &control calculation = 'vc-relax' restart_mode = 'from_scratch' prefix = 'si' tprnfor = .true. wf_collect = .true. pseudo_dir = '/usr/local/espresso/espresso-5.0.3/pseudo/' outdir = '/fs/lustre/osu7834/si/' / &system ibrav = 0 nat = 2 ntyp = 1 ecutwfc = 25.0 / &electrons conv_thr = 1.0d-7 diagonalization = 'cg' / &IONS / &CELL cell_factor = 1.6 / CELL_PARAMETERS {bohr} 10.40 0.00 0.00 0.00 10.40 0.00 0.00 0.00 10.40 ATOMIC_SPECIES Si 28 Si.pbe-n-van.UPF ATOMIC_POSITIONS {crystal} Si -0.25 0.75 -0.25 Si 0.00 0.00 0.00 K_POINTS {automatic} 4 4 4 0 0 0? +++++++++++++++++++++++++++++++++ Adib Samin, PhD Postdoctoral Researcher The Department of Aerospace and Mechanical Engineering The Ohio State University
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