<blockquote>
<p>If a method over-estimates your value of interest and another under-estimates it, then the answer you want can be obtained by taking a bit of both! (You may may notice this is not <em>ab initio</em>)</p>
</blockquote>
<blockquote>
<p>This is where things start to go a bit crazy: Welcome to the world of making up the answer you want to see - apparently some people call this science.</p>
</blockquote>
<p>Prof. Stewart Clark (University of Durham) on Exchange-Correlation Functionals in DFT</p>

JulianSE