Local Defects in the Thomas-Fermi-von Weiszäcker Theory of Crystals. Faizan Nazar working with Christoph Ortner Many Body Quantum Systems 21st March 2014 Motivation - Defects in Lattices Image by Kai Nordlund Perfect and Defective Crystals 3 ∞ Let R Λ = Z and let η ∈ Cc (B1/4 (0)) be non-negative and satisfy η = 1. Perfect and Defective Crystals 3 ∞ Let R Λ = Z and let η ∈ Cc (B1/4 (0)) be non-negative and satisfy η = 1. I Periodic nuclear density m0 (x) = X η(x − l). l∈Λ I Defective nuclear density X m1 (x) = η(x − l − UΛ (l)) + ρnuc def (x). l∈Λ Perfect and Defective Crystals 3 ∞ Let R Λ = Z and let η ∈ Cc (B1/4 (0)) be non-negative and satisfy η = 1. I Periodic nuclear density m0 (x) = X η(x − l). l∈Λ I Defective nuclear density X m1 (x) = η(x − l − UΛ (l)) + ρnuc def (x). l∈Λ ∞ 1. Nuclear defect - ρnuc def ∈ Cc (BR (0)), 2. Nuclear displacement - UΛ : Λ → R3 , satisfying UΛ ∈ W 1,2 (Λ): k∇UΛ k`2 (Λ) = 3 XX l∈Λ i=1 !1/2 2 |UΛ (l + ei ) − UΛ (l)| < ∞. The TFW Energy The Thomas-Fermi-von Weiszäcker energy functional is defined as Z Z Z 1 TFW 2 10/3 φ(m − u 2 ), E (u, m) = |∇u| + u + 2 3 3 R R where u ≥ 0 and −∆φ = 4π(m − u 2 ). The TFW Energy The Thomas-Fermi-von Weiszäcker energy functional is defined as Z Z Z 1 TFW 2 10/3 φ(m − u 2 ), E (u, m) = |∇u| + u + 2 3 3 R R where u ≥ 0 and −∆φ = 4π(m − u 2 ). The minimiser (u, φ) is unique and satisfies 5 − ∆u + u 7/3 − φu = 0, 3 − ∆φ = 4π(m − u 2 ). Existence and uniqueness is shown in [C/LB/L]. The minimisers of the energies are given by: Periodic (u0 , φ0 ) 7/3 −∆u0 + 53 u0 − φ0 u0 = 0, −∆φ0 = 4π(m0 − u02 ), Defective (u1 , φ1 ) 7/3 −∆u1 + 35 u1 − φ1 u1 = 0, −∆φ1 = 4π(m1 − u12 ). The minimisers of the energies are given by: Periodic (u0 , φ0 ) 7/3 −∆u0 + 53 u0 − φ0 u0 = 0, −∆φ0 = 4π(m0 − u02 ), Defective (u1 , φ1 ) 7/3 −∆u1 + 35 u1 − φ1 u1 = 0, −∆φ1 = 4π(m1 − u12 ). Additionally, for i = 0, 1 mi is smooth, hence ui , φi are also smooth. The minimisers of the energies are given by: Periodic (u0 , φ0 ) 7/3 −∆u0 + 53 u0 − φ0 u0 = 0, −∆φ0 = 4π(m0 − u02 ), Defective (u1 , φ1 ) 7/3 −∆u1 + 35 u1 − φ1 u1 = 0, −∆φ1 = 4π(m1 − u12 ). Additionally, for i = 0, 1 mi is smooth, hence ui , φi are also smooth. We apply a change of variables argument to compare (u0 , φ0 ) with (u1 , φ1 ). Residual Estimates First, we interpolate Id + UΛ from Λ to R3 . This gives a bijective deformation field Y ∈ C ∞ (R3 , R3 ) and J = det(∇Y ). Now define the predictors ue = u0 ◦ Y −1 J −1/2 , φe = φ0 ◦ Y −1 . Residual Estimates First, we interpolate Id + UΛ from Λ to R3 . This gives a bijective deformation field Y ∈ C ∞ (R3 , R3 ) and J = det(∇Y ). Now define the predictors ue = u0 ◦ Y −1 J −1/2 , φe = φ0 ◦ Y −1 . The residual terms u1 − ue, φ1 − φe satisfy 5 7/3 eu = g1 , −∆(u1 − ue) + (u1 − ue7/3 ) − φ1 u1 + φe 3 e = 4π(e −∆(φ1 − φ) u 2 − u12 ) + g2 + 4πρnuc def , where g1 , g2 satisfy for each k ∈ N kg1 kH k (R3 ) + kg2 kH k (R3 ) ≤ Ck k∇UΛ k`2 (Λ) . Main Estimate By adapting the proof of uniqueness from [C/LB/L], we obtain Theorem For each k ∈ N, for all ξ ∈ Cc∞ (R3 ) X Z e 2 ξ2 |∂ α (u1 − ue)|2 + |∂ α (φ1 − φ)| |α|≤k ≤ Ck X Z 2 2 |∂ α g1 |2 + |∂ α g2 |2 + |∂ α ρnuc def | ξ |α|≤k + Ck Z e 2 |∇ξ|2 . (u1 − ue)2 + (φ1 − φ) Additional Estimates I Sending ξ → 1 gives e H k (R3 ) ≤ Ck k∇UΛ k`2 (Λ) + kρnuc kH k (R3 ) . ku1 − uekH k (R3 ) + kφ − φk def Additional Estimates I Sending ξ → 1 gives e H k (R3 ) ≤ Ck k∇UΛ k`2 (Λ) + kρnuc kH k (R3 ) . ku1 − uekH k (R3 ) + kφ − φk def I Suppose that |∇UΛ (l)| ≤ C (1 + |l|)−d , then −d e |(u1 − ue)(x)| + |(φ1 − φ)(x)| ≤ C (1 + kρnuc . def kL2 (R3 ) )(1 + |x|) Additional Estimates I Sending ξ → 1 gives e H k (R3 ) ≤ Ck k∇UΛ k`2 (Λ) + kρnuc kH k (R3 ) . ku1 − uekH k (R3 ) + kφ − φk def I Suppose that |∇UΛ (l)| ≤ C (1 + |l|)−d , then −d e |(u1 − ue)(x)| + |(φ1 − φ)(x)| ≤ C (1 + kρnuc . def kL2 (R3 ) )(1 + |x|) I Alternatively, suppose UΛ (l) = 0 for |l| > R, then there exists γ > 0 such that −γ|x| e |(u1 − ue)(x)| + |(φ1 − φ)(x)| ≤ CR k∇UΛ k`2 (Λ) + kρnuc . def kL2 (R3 ) e Consider the two energy differences E 0 (VΛ ) = E TFW (uV , mV ) − E TFW (u0 , m0 ), TFW E def (VΛ ) = E TFW (uV , mV + ρnuc (u0 , m0 ). def ) − E They are well-defined for any VΛ ∈ W 1,2 (Λ) |E 0 (VΛ )| ≤ C k∇VΛ k`2 (Λ) , |E def (VΛ )| ≤ C (k∇VΛ k`2 (Λ) + kρnuc def kL2 (R3 ) ). Similarly, we can also estimate the forcing and Hessian for both E 0 , and E def . Outlook We wish to show the existence of a local minimiser UΛ of E def and prove decay estimates for UΛ . Outlook We wish to show the existence of a local minimiser UΛ of E def and prove decay estimates for UΛ . Thanks for your attention!