- The elastic and thermal properties of alkali metals are analyzed from the viewpoint of effective ion-ion interaction in rectilinear space. Consideration is given to the approximation of pair interaction between ions. The atomic-interaction potential is calculated on the basis of the pseudopotential method. Numerical calculations are made of the elastic constants, the second and fourth moments of the frequency spectrum, the temperature dependence of the Debye temperature, the specific heat, and the vibrational free energy of Na, K, Rb, and Cs. The calculations are in good agreement with the experimental values. The influence of exchange-correlation effects on the given properties is discussed. The results obtained indicate that the pseudopotential method may be successfully used for the calculation of the thermodynamic properties of metals by a traditional scheme, restricting consideration to the first two coordination spheres.