<div dir="ltr">Dear Wien2k users:<br><br><span class="gmail-" id="gmail-result_box" lang="en"><span class="gmail-">In a recently 
published work using Hybrid Funtional I read that the authors have optimized the </span></span><span class="gmail-" id="gmail-result_box" lang="en"><span class="gmail-"><span class="gmail-st">fraction of exact exchange </span>but I 
did not understand how to choose its optimal value</span><br><span class="gmail-"><br>My question is how to optimize the </span></span><span class="gmail-st">fraction of exact exchange (alpha)<em>.<br></em></span></div>