Table 1 Mathematical equations and symbols of chosen alloy descriptors.

From: Designing of high entropy alloys with high hardness: a metaheuristic approach

S.no.

Descriptor

Formula

1

Average values of elemental descriptors

\(p= \sum_{i=1}^{n}XiPi\)

Xi = elemental composition of ith element, Pi = elemental properties of ith element

2

Standard deviation

\(\updelta = \sqrt{\sum Xi{(1-\frac{Pi}{P})}^{2}}\)

3

Atomic volume24

\(Vm= \sum_{i=1}^{n}Xi(\frac{4}{3}{\pi r}^{3})\)

4

Mixing entropy17

\(Smix= -R\sum_{i=1}^{n}Xi{\text{ln}}Xi\) R = 8.31* 10–3 kJ/Mol

5

Mixing enthalpy25

\(Hmix=4\sum_{i=1 ,j\ne 1}^{n}\Delta Hij Xi Xj\)

6

Gibbs free energy

\(Gmix=Hmix-TavgSmix\)

7

Average temperature21

\(Tavg= \sum_{i=1}^{n}XiTmi\)

8

Combination effect-121

\(\Omega = \frac{TavgSmix}{\left|Hmix\right|}\)

9

Combination effect-2 (\(\Lambda\))23

\(\Lambda = \frac{Smix}{({\delta }_{r}{)}^{2}}\)

10

Ď’22

\(\Upsilon =(1-\frac{\sqrt{\frac{\left({\text{min}}\left\{ri\right\}+{r}^{2}\right)-{r}^{2}}{({\text{min}}\left\{ri\right\}+r{)}^{2}}}}{\sqrt{\frac{\left({\text{max}}\left\{ri\right\}+{r}^{2}\right)-{r}^{2}}{({\text{max}}\left\{ri\right\}+r{)}^{2}}}})\)

11

Valency electron difference20

\(\mathrm{\Delta VEC}= \sqrt{\sum_{i=1}^{n}Xi(VEC-VECi{)}^{2}}\)