Assessing the structural stability and vibration properties in beryllium selenide from the (3D) bulk, the (0D) molecule, the (2D) monolayer to the (1D) single walled nanotubes through ab initio simulations

An extensive computational study of beryllium selenide (BeSe) in different arrangements from molecule, bulk, monolayer (h-BeSe), to the single-walled zigzag (n,0) and armchair (n,n) nanotubes (SWBeSeNTs) has been carried out using a combination of ab initio quantum mechanical methods. For the molecule, the electronic computations have been performed using highly correlated ab initio methods, here at the multiconfiguration selfconsistent field and multireference configuration interaction level including the Davidson correction (MRCI+Q) in conjunction with the aug-cc-pV5Z basis set as implemented in the MOLPRO program. Accurate potential energy curves of BeSe were generated for the electronic ground state and excited states. A set of vibrational spectroscopic parameters is derived. For the periodic arrangements, structural parameters, phonon frequencies, IR and Raman intensities, and elastic constants are computed via density functional theory with the B3LYP hybrid functional and a Gaussian basis set as implemented in the periodic ab initio CRYSTAL17 code. All results may help in unraveling the different BeSe arrangements when dimensionality reduction occurs.