free continuum states- are these ever included?

[mike marchywka]

Looking at some earlier work on hydrogen the authors suggest the free unbound

continuum states are important to getting the right answer.  Are these ever

considered in current codes ? All I've seen is number of states and maybe something

about the vacuum level. IIRC in the equation-of-motion codes the continuum was

a problem.  Does this contribution go away in larger molecules or infinite periodic

solids? 

https://lucris.lub.lu.se/ws/portalfiles/portal/1680197/2968980.pdf

https://www.researchgate.net/profile/Yasutami-Takada/publication/243566114_Strong_Electron_Correlation_in_a_Localized_State_Described_in_Terms_of_Extended_States_General_Formulation_and_Illustration_in_a_Helium_Atom/links/544ef00a0cf29473161becb5/Strong-Electron-Correlation-in-a-Localized-State-Described-in-Terms-of-Extended-States-General-Formulation-and-Illustration-in-a-Helium-Atom.pdf