Electric field gradients in MgB sub(2) synthesized at high pressure: super(111)Cd TDPAC study and ab initio calculation

We report the high-pressure synthesis of novel superconductor MgB sub(2) and some related compounds. The superconducting transition temperature of our samples of MgB sub(2) is found to be 36.6 K. The MgB sub(2) lattice parameters determined via X-ray diffraction are in excellent agreement with results of our ab initio calculations. The TDPAC measurements of super(111)Cd quadrupole frequency nu sub(Q) demonstrate a small increase in nu sub(Q) with decreasing temperature from T sub(room) to T sub(He). The electric field gradient V sub(zz) at the B site calculated from first principles is in fair agreement with V sub(zz) obtained from super(11)B NMR spectra of MgB sub(2) reported in the literature. It is also very close to V sub(zz) found in our super(111)Cd TDPAC experiments, which suggests that the super(111)Cd probe substitutes for boron in the MgB sub(2) lattice. copyright 2001 Elsevier Science Ltd.