CuInSe₂ synthesized by a modified solvothermal route could be altered considerably by controlling the reaction temperature, reaction time and washing agents. Synthesized CuInSe₂ powders were characterized by X-ray diffraction. The thermal properties of lattice strain (ε), particle size (t), lattice parameters (a, c) and Debye-Waller factor (B) were determined from the half-widths and integrated intensities of the Bragg reflections. CuInSe₂ powder was strained by Temperature values 150 ^ºc, 160 ^ºc, 170 ^ºc, 180 ^ºc and 190 ^ºc. From a study of X-ray diffractograms recorded at different stages of different temperature values, it is observed that it has systematic effect on the particle size.The particle shape was spherical when deionized water was used as washing agent and Particles with the size down to 26.6nm were obtained. When the washing agent changed to ethanol, nano-rods with the diameter ranged from 100 to 200nm and the length of several micrometer were observed in the TEM. The variation of energy of vacancy formation as a function of lattice strain has been studied.