Convergence problems on HCP and BCC primitive unit cells when number of cores > 1
Posted: Tue Dec 20, 2011 9:31 pm
Hello,
I have recently started using VASP again after ~ a 2.5 year hiatus. As a first task, I am converging some bulk metal structures, e.g., for Ru, which is HCP. I am using VASP 5.2.
I set up a POSCAR according to experimental crystal data (Ru-Ru distances ~ 2.7 Angstroms). The primitive unit cell has lattice vectors of (0.5, -sqrt(3)a/2, 0); (0.5, sqrt(3)a/2, 0); (0,0,c), where a ~ 2.7, and c ~ 1.6a. It has 2 Ru atoms at fractional coordinates of (1/3,2/3,1/4) & (2/3,1/3,3/4). I used a gamma centered KPOINT mesh with > 160 irreducible k-points, and the following flags (amongst others, which I will elaborate on if necessary) in the INCAR:
IALGO = 48 -or- default value
ALGO = Normal -or- fast
LREAL = .FALSE.
IBRION = 1
NFREE = 10
POTIM = 0.1
NPAR = 1
LPLANE = .TRUE.
NSIM = 10 -or- 8
Oddly, if I run this simulation on a single core, the simulation finishes without errors. If I run across all 24 cores on the same node, I get errors, e.g., such as the following:
WARNING: Sub-Space-Matrix is not hermitian in DAV
I am running this simulation on Linux nodes with quad hexacore Intel Xeon processors. My vasp executable uses the MIT FFTW and MKL BLAS and LAPACK libraries, but I have tried executables that use the default LAPACK libraries and gotten the same errors. (I can share more details about my compilation if it will be useful.)
Interestingly, I do not get the same errors when I run simulations on FCC primitive unit cells.
I found several hits on this forum containing the same error message that I'm getting, but none of them seems to be solved by running on 1 core vs. multiple. I did find one other result (http://cst-www.nrl.navy.mil/users/erwin ... s/#notherm) that may be related.
Any advice on why I am getting this error?
Thank you very much.
I have recently started using VASP again after ~ a 2.5 year hiatus. As a first task, I am converging some bulk metal structures, e.g., for Ru, which is HCP. I am using VASP 5.2.
I set up a POSCAR according to experimental crystal data (Ru-Ru distances ~ 2.7 Angstroms). The primitive unit cell has lattice vectors of (0.5, -sqrt(3)a/2, 0); (0.5, sqrt(3)a/2, 0); (0,0,c), where a ~ 2.7, and c ~ 1.6a. It has 2 Ru atoms at fractional coordinates of (1/3,2/3,1/4) & (2/3,1/3,3/4). I used a gamma centered KPOINT mesh with > 160 irreducible k-points, and the following flags (amongst others, which I will elaborate on if necessary) in the INCAR:
IALGO = 48 -or- default value
ALGO = Normal -or- fast
LREAL = .FALSE.
IBRION = 1
NFREE = 10
POTIM = 0.1
NPAR = 1
LPLANE = .TRUE.
NSIM = 10 -or- 8
Oddly, if I run this simulation on a single core, the simulation finishes without errors. If I run across all 24 cores on the same node, I get errors, e.g., such as the following:
WARNING: Sub-Space-Matrix is not hermitian in DAV
I am running this simulation on Linux nodes with quad hexacore Intel Xeon processors. My vasp executable uses the MIT FFTW and MKL BLAS and LAPACK libraries, but I have tried executables that use the default LAPACK libraries and gotten the same errors. (I can share more details about my compilation if it will be useful.)
Interestingly, I do not get the same errors when I run simulations on FCC primitive unit cells.
I found several hits on this forum containing the same error message that I'm getting, but none of them seems to be solved by running on 1 core vs. multiple. I did find one other result (http://cst-www.nrl.navy.mil/users/erwin ... s/#notherm) that may be related.
Any advice on why I am getting this error?
Thank you very much.