Encapsulation of lawrencium into C60 fullerene: Lr@C60 versus Li@C60

The position of Lawrencium (Lr) in the periodic table has been debated several times. It has been noticed that some fundamental properties of Lr differ from the other elements of the actinide series and closely resemble those of alkali metal. To be specific, the first ionization energy of Lr 4.96 eV [Nature 520 (2015) 209] lies within the range assigned to alkali metals. Motivated by this fact, we study Lr@C-60 for the first time and compared its electronic properties with those of Li@C-60. Using density functional theory and its time dependent version, we explore structures, vibrational infrared spectra, molecular orbital surfaces, density of states and electronic absorption spectra of Lr@C-60 and Li@C-60. We notice that although Lr resides very close to the centre of C-60 than Li does, the electronic properties of Lr@C-60 closely resemble those of Li@C-60. For instance, Lr@C-60 is as conducting and polarizable as Li@C-60 due to almost equal frontier orbital energy gap and mean polarizability. This study is expected to provide further evidence where Lr atom mimics the alkali metal. (C) 2016 Elsevier B.V. All rights reserved.