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Publication

Density Functional Steric Analysis of Lineaer and Branched Alkanes

Journal Contribution - Journal Article

Branched alkane hydrocarbons are thermodynamically more stable than straight-chain linear alkanes. This thermodynamic stability is also manifest in alkane bond separation energies. To understand the physical differences between branched and linear alkanes, we have utilized a novel density functional theory (DFT) definition of steric energy based on the Weizäcker kinetic energy. Using the M06-2X functional, the total DFT energy was partitioned into a steric energy term (Es[ρ]), an electrostatic energy term (Ee[ρ]), and a fermionic quantum energy term (Eq[ρ]). This analysis revealed that branched alkanes have less (destabilizing) DFT steric energy than linear alkanes. The lower steric energy of branched alkanes is mitigated by an equal and opposite quantum energy term that contains the Pauli component of the kinetic energy and exchange-correlation energy. Because the steric and quantum energy terms cancel, this leaves the electrostatic energy term that favors alkane branching. Electrostatic effects, combined with correlation energy, explains why branched alkanes are more stable than linear alkanes.
Journal: J.Chem.A
ISSN: 1089-5639
Issue: 49
Volume: 114
Pages: 12952–12957
Publication year:2010
Keywords:Density Functional Steric Analysis
  • ORCID: /0000-0003-4900-7513/work/71140136