A cautionary note on the use of the frozen-core approximation for correlation energy calculations involving alkali metals

1990 ◽  
Vol 11 (10) ◽  
pp. 1147-1150 ◽  
Author(s):  
Heinz Hofmann ◽  
Elke Hünsele ◽  
Timothy Clark
Keyword(s):  
Alkali Metals ◽  
Correlation Energy ◽  
Cautionary Note ◽  
Energy Calculations ◽  
Core Approximation

scholarly journals Graphite as A Hydrogen Storage in Fuel Cell System: Computational Material Study for Renewable Energy

2017 ◽  
Vol 17 (2) ◽  
pp. 103
Author(s):  
Rahmat Gunawan ◽  
Cynthia Linaya Radiman ◽  
Muhamad Abdulkadir Martoprawiro ◽  
Hermawan K. Dipojono
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Storage ◽  
Density Functional ◽  
Alkali Metals ◽  
Correlation Energy ◽  
Atomic Orbital ◽  
Hydrogen Gas ◽  
Basis Set ◽  
Functional Theory ◽  
Orbital Contribution

The Hydrogen storage based-graphite materials have been investigated theoretically via Density Functional Theory (DFT) approach. The native graphite was compared to the modified graphite, namely the intercalation graphite (GICs, graphite intercalated compounds). Here the GICs was intercalated by alkali metals (Li, Na and K). The electronic structures, energetics and atomic orbital contributions of hydrogen-graphite system, GICs, and hydrogen-GICs were studied by calculation approach of gradient corrected PBE (Perdew-Burke-Ernzerhof) for recovery of exchange-correlation energy. The calculation was supported by using basis set of the plane waves whereas the computation of electron-core by using Ultrasoft Vanderbilt pseudopotential. The computational calculation provides four main studies i.e. molecular geometry relaxation, determination of electronic bands structure of energy, energy state density (DOS) and atomic orbital contribution by charge density differences.Keywords: Density Functional Theory, hydrogen gas, graphite intercalated material

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