PRESSURE-INDUCED S-]D TRANSFER AND THE EQUATION OF STATE OF MOLYBDENUM

The equations of state of crystalline (bcc) and liquid molybdenum are calculated to pressure-temperature conditions of 600 GPa and 14 000 K with use of the linear muffin-tin orbitals (LMTO) model and corrected rigid-ion sphere (CRIS) model. Our results agree with those of previous work in documenting a pressure-induced shift of electrons from 5s to 4d states, especially above 100 GPa. An analysis of ultrasonic and shock-wave measurements, along with our theoretical findings, documents that the compressibility of bcc Mo becomes enhanced at pressures of 100e"200 GPa. The enhanced compression, and possibly an anomalous increase in rigidity, are caused by the pressure-induced s'd transfer. Our study reinforces the use of the Mo equation of state as a calibration standard for ultrahigh-pressure static experiments and, in particular, for the ruby-fluorescence technique. © 1990 The American Physical Society.