$$\Delta H$$
() Q α / 0 α 0 (ea H, s w -H, s 0 ) ≈ α (H, s w  -H, s ) +     ΔH (ea H) AH K H α Ξ /ea H\ K но
$$\phi$$
K H α L n kn AH α n kn AH ΔH Q n d kn AH n Z a
$$\mathbf{l}$$
z AH z +  nkn AH + T+ Tki V k AH ΔH l + Q£ 0 £££ . Z  z + ∑ n kn ∆ H 8
N

## 4.1  First Order And The Variational Bound

Z + (ΔH) + − k 5 ΔH Z