Topics

1

General Questions and Answers / Very slow Ni convergence

« on: September 1, 2010, 09:33 »

I have problems with the convergence of a Ni system consisting of 90 atoms configured in a two layer slab model with some vacuum space in between. I'm using the double zeta polarized basis set (also tried the double zeta double polarized set, without improvement) and tried several different values for the k point sampling (from 4, 4, 1 to 10, 10, 1 with increments of 2). I also tried extending the cut-off energy from the default 75 Hartree to 150 Hartree. Decreasing the electron temperature to 10 K gave no improvement. However, when I increased the temperature to 1000 K for the first time the system converged within 100 steps (to be precise: in 98 steps using k=661 and a cut-off of 150 Hartree). When I increased the k points to 8, 8, 1 the system didn't convergence within 100 steps, however.

Are there more settings I could try to speed up convergence? I used a similar system for Cu, Pd and Al and none of those materials had convergence issues (although Pd took about 60 steps to convergence vs ~30 for Cu and Al). I want to optimize the geometry of this system, and that is going to take ages if the system converges this slow.

I attached the configuration to my post.

2

General Questions and Answers / Strange GUI behaviour

« on: December 4, 2009, 16:11 »

When following some of the available tutorials for VNL 2008.10 I came across several strange things that are happening in the VNL GUI:
1. I use a dual-screen setup on my Linux system, and somehow VNL doesn't correctly detect my screen size and makes the fonts huge. This really scrambles the VNL GUI. It doesn't prevent one from working with the program, but it is rather annoying. Is there something that can be done to make VNL detect my display settings correctly? Or is this a nVidia bug.
2. I did part of the graphene tutorial form the website and when I display the results from the transmission spectrum in the result browser the figure is horrible. The transmission axis only runs from 0 to 1, while the actual transmission can be as large as 4 as indicated in the tutorial. Is there a way to rescale the plot? All that the result browser seems to allow is zooming in and out... which is rather limited. Is there a way to expert the plot data so that I can edit it in, say, SigmaPlot?

Some system details:
openSUSE 11.2 x86-64 running KDE 4.3.1
nVidia twinview

See the attached image for a screenshot of the program.

3

Installation and License Questions / Error installing VNL under openSUSE 11.2

« on: November 16, 2009, 15:09 »

Hi,

I'm trying to install VNL 2008.10 under openSUSE 11.2 x86-64. I found that some libraries were missing (gcc, glibc-devel and gcc-g77). I installed the 32 bit versions of those three (which means I also need the 64 bit version of the gcc and glibc-devel). After this the libg2c error was gone, but now when I try to run vnl I get the following error:

vnl: line 3: 25858 Segmentation fault      LD_LIBRARY_PATH=$EXEC_DIR/../lib $EXEC_DIR/vnl_exec $*

What is this (it seems to be related with a program attempting to do something to a memory location it isn't allowed), and more important: how can I fix this?