Exchange-correlation effect in the charge response of a warm dense electron gas

The study of warm dense matter, widely existing in nature and laboratories, is challenging due to the interplay of quantum and classical fluctuations. We develop a variational diagrammatic Monte Carlo method and determine the exchange-correlation kernel KXC(q;T) of a warm dense electron gas for a broad range of temperature T and momentum q. We observe several interesting physics, including the T-dependent evolution of the hump structure and the large-q tail and the emergence of a scaling relation. Particularly, by deriving an analytical form for q→∞, we obtain large-q tails of KXC with high precision. It is shown that the KXC data can be reliably transformed into real space, which can be directly used in density-functional-theory calculations of real warm dense matter.