Equilibrium mechanical unfolding of a globule formed by long flexible homopolymer chain collapsed in a poor solvent and subjected to an extensional force f (force-clamp mode) or extensional deformation D (position-clamp mode) is studied theoretically. Our analysis, like all previous analysis of this problem, shows that the globule behaves essentially differently in two modes of extension. In the force-clamp mode, mechanical unfolding of the globule with increasing applied force occurs without intramolecular microphase segregation, and at certain threshold value of the pulling force the globule unfolds as a whole ("all-or-none" transition). The value of the threshold force and the corresponding jump in the distance between the chain ends increase with a deterioration of the solvent quality and / or with an increase in the degree of polymerization. In the position-clamp mode, the globule unfolding occurs via intramolecular microphase coexistence of globular and extended microphases followed by an abrupt unraveling transition. Reaction force in the microphase segregation regime demonstrates an "anomalous" decrease with increasing extension. Comparison of deformation curves in force and position-clamp modes demonstrates that at weak and strong extensions the curves for two modes coincide, differences are observed in the intermediate extension range. Another unfolding scenario is typical for short globules: in both modes of extension they unfold continuously, without jumps or intramolecular microphase coexistence, by passing a sequence of uniformly elongated configurations. The values of the the critical chain length, Ncr, separating long and short chain behavior are slightly different for two extension modes: N cr,f < Ncr,D.
Summary:We propose the quantitative mean-field theory of mechanical unfolding of a globule formed by long flexible homopolymer chain collapsed in poor solvent and subjected to an extensional force We show that with an increase in the applied force the globule unfolds as a whole without formation of an intermediate state. The value of the threshold force and the corresponding jump in the distance between chain ends increase with a deterioration of the solvent quality and / or with an increase in the degree of polymerization. This way of globule unfolding is compared with that in the D-ensemble, when the distance between chain ends is imposed.
Ab initio calculations were performed to investigate composition dependences of crystal lattice parameters, magnetic moments,bulk modulus, magnetic exchange parameters inNi2-yCoyMn1.5-xCrxSn0.5 (y =0.2, 0.4; 0.0 ≤ x ≤ 0.4) Heusler alloys. It was shown that increasing of Cr content (x) firstly leads an increasing of lattice parameter, but then a decreasing. The strongest ferromagnetic (FM) interaction for Ni1.6Co0.4Mn1.4Cr0.1Sn0.5 is nearest-neighbor interaction between Co and Mn1 (on own sites). The strongest antiferromagnetic (AFM) interaction is observed between nearest-neighbor Mn1-Cr atoms in the first coordination sphere and it is equal to-15 meV. Total magnetic moment of Ni2-yCoyMn1.5-xCrxSn0.5 (y =0.2, 0.4; 0.0 ≤ x ≤ 0.4) takes value in region from 6.1 μB to 6.6 μB.
Abstract. The composition dependences of crystal lattice parameters, bulk modulus, magnetic moments, magnetic exchange parameters in Ni2-yCoyMn1.5-xCrxSn0.5 (y = 0.2, 0.4; 0.0 x 0.4) Heusler alloys are investigated with the help of ab initio calculations. Our simulations have shown that crystal lattice parameter firstly increased and then decreased with Cr content (x) increasing. The strongest ferromagnetic interaction for Ni1.6Co0.4Mn1.4Cr0.1Sn0.5 is nearest-neighbor interaction between Co and Mn1 (on own sites). The strongest antiferromagnetic interaction is observed between nearest-neighbor Mn1-Cr atoms in the first coordination sphere and it is equal to -15meV. Total magnetic moment of Ni2-yCoyMn1.5-xCrxSn0.5 (y =0.2, 0.4; 0.0 x 0.4) takes value in region from 6.1 μB to 6.6 μB.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.