Current-density functional study of the HeH plus molecular ion under a strong ultrashort magnetic field

The HeH+ molecular ion under an ultrashort magnetic field on the order of 109 G is investigated through quantum fluid dynamics and a current-density functional theory (CDFT) based approach, employing a vector exchangecorrelation (XC) potential which depends on the electronic charge-density as well as on the current-density. The behavior of the exchange and correlation energies of the HeH+ ion is analyzed and compared with those obtained using an approach based on the time-dependent density functional theory (TD-DFT) under similar computational constraints but employing a scalar XC potential dependent only on the electronic charge-density. The CDFT-based approach yields exchange and correlation energies as well as TD electronic charge-densities drastically different from those obtained using the TD-DFT-based approach particularly, at typical TD magnetic field strengths. This is attributed to the nonadiabatic effects induced by the vector XC potential of the CDFT in the oscillating charge-density of the HeH+ ion, which are further explained in the terminology of quantum fluid dynamics. The vector XC potential of the CDFT-based approach is observed to augment the magnetic interactions in the H2 molecule and in the He?22+ ion, whereas it opposes the magnetic interactions in the HeH+ ion particularly, at the intermediate magnetic field strengths. (C) 2012 Wiley Periodicals, Inc.