Gradients for twocomponent quasirelativistic methods. Application to dihalogenides of element 116
Abstract
The authors report the implementation of geometry gradients for quasirelativistic twocomponent HartreeFock and density functional methods using either the zeroorder regular approximation Hamiltonian or spindependent effective core potentials. The computational effort of the resulting program is comparable to that of corresponding nonrelativistic calculations, as it is dominated by the evaluation of derivative twoelectron integrals, which is the same for both types of calculations. Besides the implementation of derivatives of matrix elements of the oneparticle Hamiltonian with respect to nuclear displacements, the calculation of the derivative exchangecorrelation energy for the open shell case involves complicated expressions because of the noncollinear approach chosen to define the spin density. A pilot application to dihalogenides of element 116 shows how spinorbit coupling strongly affects the chemistry of the superheavy pblock elements. While these molecules are bent at a scalarrelativistic level, spinorbit coupling is so strong that only the 7p_{3/2} atomic orbitals of element 116 are involved in bonding, which favors linear molecular geometries for dihalogenides with heavy terminal halogen atoms.
 Publication:

Journal of Chemical Physics
 Pub Date:
 March 2007
 DOI:
 10.1063/1.2711197
 Bibcode:
 2007JChPh.126k4106V
 Keywords:

 31.15.Ne;
 31.15.Ew;
 31.30.Jv;
 33.15.Bh;
 33.15.Fm;
 Selfconsistentfield methods;
 Densityfunctional theory;
 Relativistic and quantum electrodynamic effects in atoms and molecules;
 General molecular conformation and symmetry;
 stereochemistry;
 Bond strengths dissociation energies