Nuclear quadrupole interactions at W-187(beta-)Re-187 in ZrW2O8

In ZrW2O8, a material with negative thermal expansion, two nuclear quadrupo le interactions at W-187(beta(-)) Re-187 with equal populations were determ ined by time differential perturbed angular correlation to be (at 295 K): n u(Q1) = 336(1) MHz, eta(1) = 0 and nu(Q2) = 1391(2) MHz, eta(2) = 0.053(4). The nuclear quadrupole interactions are assigned to two crystallographical ly distinct tungsten sites. These results are the bases for further TDPAC s tudies of the negative thermal expansion on a microscopic scale.