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General derivation of the well-known Ren–Otsuka relationship, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mstyle scriptlevel="0" displaystyle="true"><mfrac><mrow><mn>1</mn></mrow><mrow><mi>α</mi></mrow></mfrac></mstyle><mstyle scriptlevel="0" displaystyle="true"><mfrac><mrow><mi>d</mi><msub><mrow><mi>T</mi></mrow><mrow><mi>o</mi></mrow></msub></mrow><mrow><mi>d</mi><mi>x</mi></mrow></mfrac></mstyle><mo>=</mo><mo>−</mo><mstyle scriptlevel="0" displaystyle="true"><mfrac><mrow><mi>α</mi></mrow><mrow><mi>β</mi></mrow></mfrac></mstyle></mrow></semantics></math></inline-formula> (where <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>T</mi></mrow><mrow><mi>o</mi></mrow></msub></mrow></semantics></math></inline-formula>, <i>x</i>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>α</mi></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>β</mi><mo>(</mo><mo>></mo><mn>0</mn><mo>)</mo></mrow></semantics></math></inline-formula> are the transformation temperature and composition, as well as the composition and temperature coefficient of the critical shear constant, <i>c</i>′, respectively) for shape memory alloys, SMAs, is provided based on the similarity of interatomic potentials in the framework of dimensional analysis. A new dimensionless variable, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>t</mi></mrow><mrow><mi>o</mi></mrow></msub><mfenced separators="|"><mrow><mi>x</mi></mrow></mfenced><mo>=</mo><mstyle scriptlevel="0" displaystyle="true"><mfrac><mrow><msub><mrow><mi>T</mi></mrow><mrow><mi>o</mi></mrow></msub><mfenced separators="|"><mrow><mi>x</mi></mrow></mfenced></mrow><mrow><msub><mrow><mi>T</mi></mrow><mrow><mi>m</mi></mrow></msub><mfenced separators="|"><mrow><mi>x</mi></mrow></mfenced></mrow></mfrac></mstyle></mrow></semantics></math></inline-formula>, describing the phonon softening (where <i>T_m</i> is the melting point) is introduced. The dimensionless values of the heat of transformation, Δ<i>H</i>, and entropy, Δ<i>S</i>, as well as the elastic constants <i>c</i>′, <i>c</i>₄₄, and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>A</mi><mo>=</mo><mstyle scriptlevel="0" displaystyle="true"><mfrac><mrow><msub><mrow><mi>c</mi></mrow><mrow><mn>44</mn></mrow></msub></mrow><mrow><msup><mrow><mi>c</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></mfrac></mstyle></mrow></semantics></math></inline-formula> are universal functions of <i>t_o</i>(<i>x</i>) and have the <b>same constant</b> values at <i>t_o</i>(0) within sub-classes of host SMAs having the same type of crystal symmetry change during martensitic transformation. The ratio of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mstyle scriptlevel="0" displaystyle="true"><mfrac><mrow><mi>d</mi><msub><mrow><mi>t</mi></mrow><mrow><mi>o</mi></mrow></msub></mrow><mrow><mi>d</mi><mi>x</mi></mrow></mfrac></mstyle></mrow></semantics></math></inline-formula> and <i>α</i> has the same constant value for all members of a given sub-class, and relative increase in <i>c</i>′ with increasing composition should be compensated by the same decrease in <i>t_o</i>. In the generalized Ren–Otsuka relationship, the anisotropy factor <i>A</i> appears instead of <i>c</i>′, and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>α</mi></mrow></semantics></math></inline-formula> as well as <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>β</mi></mrow></semantics></math></inline-formula> are the differences between the corresponding coefficients for the <i>c</i>₄₄ and <i>c</i>′ elastic constants. The obtained linear relationship between <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>h</mi></mrow></semantics></math></inline-formula> and <i>t_o</i> rationalizes the observed empirical linear relationships between the heat of transformation measured by differential scanning calorimetry (DSC) (<i>Q^A</i>^⟶<i>M</i>) and the martensite start temperature, <i>M_s</i>.