In this exercise, you will first perform simple scf (self-consistent field) calculations on silicon.
Enter the directory ex1. You will see the following files:

For each calculation that you will run, you can use as a template that you can copy to another file and then edit. Alternatively, you can use shell scripts to automate this process.

First you need to login on to your specific node (you will have been told what this is). I suggest opening a second terminal window to do this. (X - the way to dispay graphical programs remotly only works on the head node. So I suggest two windows - one open on the head node, one on the compute node)

 [Student-16:~] che721% ssh -Y
 Last login: Mon Sep 21 14:10:23 2009 from
 Have a lot of fun...
 tuto01@cecamsrv4:~> ssh node09
 ssh: node09: Name or service not known
 tuto01@cecamsrv4:~> ssh node009
 The authenticity of host 'node009 (' can't be established.
 RSA key fingerprint is 28:18:f0:9e:ca:7d:c2:23:d9:75:94:89:f2:6a:c2:05.
 Are you sure you want to continue connecting (yes/no)? yes
 Warning: Permanently added 'node009,' (RSA) to the list of known hosts.
 Have a lot of fun...

Use Xcrysden to view the structure in the sample input file:

xcrysden --pwi

Play around with xcrysden! Rotate the view, display the boundaries of the conventional cubic cell, etc.

Run an scf calculation:

The way to do this is:

pw.x < input_filename > output_filename

So in this particular case, you will type:

pw.x < > Si.sample.out

Read the output, and answer the following questions:

(Note: you can find this by looking for an exclamation mark in the output file). For example, you can type:

      grep ! Si.sample.out

Note: If you set verbosity = 'high' in the &control namelist, you will get additional information in your output file, e.g., about symmetries and occupation numbers.

Convergence tests with respect to plane-wave cut-off:

Find out how the total energy changes when you vary the plane wave cut-off ecutwfc between 10 and 30 Ry, in steps of 5 Ry. You can either do this by copying the sample file to other input files and editing them, and running pw.x using each of these input files in turn, or by running the sample shell script


Now make a data file (e.g., you can call it etotvsecut.dat) that contains the value of ecutwfc in the first column, and total energy in the second column. Remember that you can easily find the values of the total energy by searching for an exclamation mark, e.g., using the grep command.

Plot a graph of this data using your favorite plotting program (e.g., xmgrace or gnuplot).

Convergence with respect to Brillouin zone sampling: