Vapor pressure and thermodynamics of Bk-249 metal

Abstract
The vapor pressure of 249Bk metal has been measured over the range 1100–1500 K, using combined target and mass spectrometric Knudsen effusion techniques. Vapor pressure data are combined with an appropriate estimate for the solid heat capacity and the estimated crystal entropy S°298, to produce enthalpy, entropy, and free energy functions from 298 to 2000 K. The vapor pressures are described by the equations: Log10 P(atm) = −(15 718 ±253)/T+578±0.21 [solid, 1107–1319 K], Log10 P(atm) = −(14 902 ±244)/T+5.14±0.17 [liquid, 1345–1528 K] from which we calculate Δ H°298 (2nd law) = 73 960±1150 cal/mol [solid], Δ H°298 (2nd law) = 73 980±1120 cal/mol [liquid], and Δ H°298 (3rd law) = 74 220±180 cal/mol [solid and liquid].

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