Temperature dependences of the resistivity and Hall coefficient of untwinned single-crystal ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ at constant volume

The previously published constant-pressure temperature dependences of the resistivity eigenvalues and Hall coefficient of untwinned single-crystal ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ are used, together with the coefficient of expansion and the compressibility, to calculate the constant-volume temperature dependences of these transport coefficients, since the constant-volume values are the quantities that have been predicted by theories of high-temperature superconductivity. It is found that the in-plane resistivity eigenvalues at constant volume are slightly lower and more nearly linear in the temperature than at constant pressure. The c-axis resistivity at constant volume is also slightly lower than at constant pressure, and approximately as linear. ${\mathit{G}}_{\mathit{H}}$, the reciprocal of the Hall coefficient ${\mathit{R}}_{\mathit{H}}$, at constant volume is slightly higher and just as nearly linear in the temperature as at constant pressure. The cotangent of the Hall angle, as a function of ${\mathit{T}}^2$, is essentially the same at constant pressure as at constant volume, and remains linear in ${\mathit{T}}^2$.