1. Calculation: 
<p>
  Correct solution: see e.g. <a href="ex6_2.ps"> Tommi Järvis file </a>
<p>

  Calculating correction factor: script calccorr:
<pre>
3 -2.69845
4 -1.25671
5 -0.486338
6 -0.173105
7 -0.058639
8 -0.0191903
9 -0.00611745
10 -0.00190965
11 -0.000585955
12 -0.000177221
</pre>
2. 
<p>
Generate large enough cell to handle 12 Å cutoff:
<p>
~/md/structure/makeFCC 3.62 8 8 8 > atoms.in
<p>
The run with different cutoffs and add correction:
<pre>
	Epot		Vcorr
3.0      -1.50932        -2.69845        -4.20777
4.0      -2.11530        -1.25671        -3.37201
5.0      -3.03515        -0.486338       -3.52149
6.0      -3.39088        -0.173105       -3.56399
7.0      -3.49893        -0.058639       -3.55757
8.0      -3.52213        -0.0191903      -3.54132
9.0      -3.53521        -0.00611745     -3.54133
10.0     -3.54069        -0.00190965     -3.5426
11.0     -3.54154        -0.000585955    -3.54213
12.0     -3.54203        -0.000177221    -3.54221
</pre>
Tolerance of 0.1 eV reached by 7.0 Å without correction,
and at 5.0 with correction.
<p>
Problems: none really in bulk, but at surface would predict atoms
have Epot even in vacuum. Cutoff of course causes its own problems:
jumps in Epot if atoms cross the cutoff distance. And using
Vcorr does not help with this at all, so that should not be
an excuse for shortening the cutoff in finite T simulations.
<p>
  If density not correct (e.g. nonhomogeneous liquid) 
correction factor also misleading
<p>
Plot: <a href="epot.ps"> epot.ps </a>

<p>

3.  About stable up to deltat 10 fs, blows up for deltat >= 30 fs.
<p>
  ./mdmorse | & tee out.10fs
<p>
xgr -pick 1 ec -c 2 6 out.*
<p>
  At 10 fs still about stable, at 30 fs blows up like mad.
<p>