Effects of Stress on Superconducting Sn, In, Tl, and Al

Hydrostatic pressures of 0 to 100 atmos obtained with helium gas pressure, and of 1. 910^3 atmos obtained by an ice expansion bomb technique are used to measure the pressure displacement of critical temperature T₂. The coefficient ({T₂}) for Sn, In, Tl, and Al is -4. 70. 2, -4. 00. 2, +0. 60. 3, and -2. 00. 2 in units of 10^-5 ^/atmos, respectively. The temperature dependence of R= ({{{H₂}) }ₓ}{ ({{H₂}) }ₓ₂} above 1^ is described by R=0. 61+0. 029T^2 for Sn, and R=0. 77+0. 020T^2 for In. This result is discussed in connection with the similarity principle, H₀{T₂}=constant. From an analysis combining stress and isotope effects, it is seen that T₂, or H₂, is more sensitive to volume changes, holding zero-point lattice vibration amplitude fixed, than to zero-point amplitude changes, holding V fixed: ({{H₂}) }ₐ^{2}=5. 5 ({{H₂}{q^2}) }ₕ for Sn. Zero-pressure critical field data are also presented for the subject metals.