Quantum Monte Carlo Calculations of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">A</mml:mi><mml:mi>≤</mml:mi><mml:mn>6</mml:mn></mml:math>Nuclei

The energies of ${}^{3}\mathrm{H}$, ${}^{3}\mathrm{He}$, and ${}^{4}\mathrm{He}$ ground states, the ${\frac{3}{2}}^{{}^{\ensuremath{-}}}$ and ${\frac{1}{2}}^{{}^{\ensuremath{-}}}$ scattering states of ${}^{5}\mathrm{He}$, the ground states of ${}^{6}\mathrm{He}$, ${}^{6}\mathrm{Li}$, and ${}^{6}\mathrm{Be}$, and the ${3}^{+}$ and ${0}^{+}$ excited states of ${}^{6}\mathrm{Li}$ have been accurately calculated with the Green's function Monte Carlo method using realistic models of two- and three-nucleon interactions. The splitting of the $A\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3$ isospin $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\frac{1}{2}$ and $A\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}6$ isospin $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$, ${J}^{\ensuremath{\pi}}{\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0}^{+}$ multiplets is also studied. The observed energies and radii are generally well reproduced, however, some definite differences between theory and experiment can be identified.