Quasi-non-local gradient-level exchange-correlation approximation for metals and alloys

The flexibility of common generalized gradient approximation for the exchange-correlation energy is investigated by monitoring the equilibrium volume of transition metals. It is shown that no universal gradient-level approximation yielding consistent errors for all metals exists. Based on an element-specific optimization, the concept of quasi-non-local gradient-level approximation is introduced. The strength of the scheme is demonstrated on several transition metal alloys.