Memory Error in Density of States Analysis

[Himanshu Saini]

Hello,

I did calculation for Nano-wire to calculate the Density of States. In this process I used (1, 1, 25) K-points and I got satisfactory graph. However, when I tried again to calculate the density of states with (1, 1, 200) K-points so that the resolution of graph will be better, I got an error message "Memory Error".

So, I am requesting you to all who have a solution for this problem please reply. Since the calculation is already done for (1, 1, 200) K-points so how will I can reuse that calculation to generate DOS graph. My Laptop configurations are as follows Intel CORE i5 4th Generation processor @ 1.70GHz, NVIDIA GEFORCE Graphics Card 2GB, and 4GB RAM.

Below I am showing the output log file:

+------------------------------------------------------------------------------+
|                                                                              |
| Density of States Analysis                                                   |
|                                                                              |
+------------------------------------------------------------------------------+

                            |--------------------------------------------------|
Calculating DOS            : ating DOS            : ==================================================


Timing:                          Total     Per Step       

--------------------------------------------------------------------------------

File IO, nlread         :      14.56 s      14.56 s       0.02|=============|
Loading Modules + MPI   :       3.40 s       3.40 s       0.00|==|
--------------------------------------------------------------------------------
Total                   :   85558.13 s (23h45m58.13s)
Traceback (most recent call last):
  File "Nanowire_DOS_More K Points_200.py", line 13, in <module>
    bands_above_fermi_level=None,
  File ".\zipdir\NL\Analysis\DensityOfStates.py", line 108, in __init__
  File ".\zipdir\NL\Analysis\DensityOfStates.py", line 763, in calculateDensityOfStates
MemoryError

MemoryError

[Jess Wellendorff]

It would be easier to help if you attach the script(s) you use.
The optimum approach is this:
1) Do the SCF calculation with a good but not exaggerated k-point grid, e.g. 1x1x9.
2) Do the DOS with 1x1x200 k-points using the "Analysis from File" functionality. Use only a single MPI process in order to minimize the memory footprint. If this analysis crashes with a memory error, you need to lower the number of k-points.