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Study of pressure influence on thermal transition in spin-crossover nanomaterials.

Gudyma IV, Maksymov AIu, Ivashko VV - Nanoscale Res Lett (2014)

Bottom Line: The thermal transition accompanied by the variation of the molecular volume in nanoparticles of spin-crossover materials has been studied on the basis of microscopic Ising-like model solved using Monte Carlo methods.For considered model, we examined the spin-crossover phenomenon with applied hydrostatic pressure and thus was shown the possibility to shift transition temperature toward its room value.The obtained results of numerical simulations are in agreement with the experimental ones.

View Article: PubMed Central - PubMed

Affiliation: Department of General Physics, Chernivtsi National University, Kotsjubynskyi Str. 2, 58012, Chernivtsi, Ukraine, yugudyma@gmail.com.

ABSTRACT
The thermal transition accompanied by the variation of the molecular volume in nanoparticles of spin-crossover materials has been studied on the basis of microscopic Ising-like model solved using Monte Carlo methods. For considered model, we examined the spin-crossover phenomenon with applied hydrostatic pressure and thus was shown the possibility to shift transition temperature toward its room value. The obtained results of numerical simulations are in agreement with the experimental ones.

No MeSH data available.


Related in: MedlinePlus

The thermal hysteresis loop for system with random external action and applied pressure. Here, the black solid curve is for the system without pressure and fluctuations and is the reference. The red, blue, and pink curves are for fixed fluctuations strength ε=100 for values pΔV=0 K, pΔV=100 K, and pΔV=300 K, respectively. The dashed curves are for constant pΔV=500 K which leads to the collapse of hysteresis for the system with ε=0 (black dashed curve). The red dashed curve is for ε=100 and pΔV=500 and demonstrates the shift of threshold pΔV value leading to hysteresis collapse. The interaction constant for all cases is J=145 K.
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Fig4: The thermal hysteresis loop for system with random external action and applied pressure. Here, the black solid curve is for the system without pressure and fluctuations and is the reference. The red, blue, and pink curves are for fixed fluctuations strength ε=100 for values pΔV=0 K, pΔV=100 K, and pΔV=300 K, respectively. The dashed curves are for constant pΔV=500 K which leads to the collapse of hysteresis for the system with ε=0 (black dashed curve). The red dashed curve is for ε=100 and pΔV=500 and demonstrates the shift of threshold pΔV value leading to hysteresis collapse. The interaction constant for all cases is J=145 K.

Mentions: The more complete description of ligand field action on central transition metal ion requires to consider its instantaneous behavior where time variation of field becomes relevant. In the following study, we investigate the influence of fluctuating nature of ligand field splitting energy of spin-crossover system with applied pressure on thermal curves obtained from Monte Carlo simulations. Our starting point is Hamiltonian (5) with external field (6). The detailed investigation of transition curves for pressureless system with different statistical characteristics of stochastic term, i.e., space-time correlated fluctuations is carried out in paper [14]. Based on this approach, we consider the spin-crossover system under applied pressure. The resulting transition curves are shown in Figure 4. In the presented figure, the solid black transition curves correspond to the deterministic system with interaction constant J=145 K, described by the Hamiltonian (2). The red curves is for zero pressure and fluctuations strength ε=100. This strength is the same for other transition curves obtained for pressure pΔV=100 K (blue line) and pΔV=300 K (pink line). As it was expected, the presence of white fluctuations enlarges the hysteresis [14]. The pressure action on hysteresis loop for the system with fluctuations leads to its narrowing and, similar to the fluctuationless system, shifts the cooling and heating branches toward higher temperature. It is obvious that the action of pressure and fluctuations strength is opposite, and in such a way, it is expected that for the fluctuating system, the collapse of hysteresis takes place for higher pressure.Figure 4


Study of pressure influence on thermal transition in spin-crossover nanomaterials.

Gudyma IV, Maksymov AIu, Ivashko VV - Nanoscale Res Lett (2014)

The thermal hysteresis loop for system with random external action and applied pressure. Here, the black solid curve is for the system without pressure and fluctuations and is the reference. The red, blue, and pink curves are for fixed fluctuations strength ε=100 for values pΔV=0 K, pΔV=100 K, and pΔV=300 K, respectively. The dashed curves are for constant pΔV=500 K which leads to the collapse of hysteresis for the system with ε=0 (black dashed curve). The red dashed curve is for ε=100 and pΔV=500 and demonstrates the shift of threshold pΔV value leading to hysteresis collapse. The interaction constant for all cases is J=145 K.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4494018&req=5

Fig4: The thermal hysteresis loop for system with random external action and applied pressure. Here, the black solid curve is for the system without pressure and fluctuations and is the reference. The red, blue, and pink curves are for fixed fluctuations strength ε=100 for values pΔV=0 K, pΔV=100 K, and pΔV=300 K, respectively. The dashed curves are for constant pΔV=500 K which leads to the collapse of hysteresis for the system with ε=0 (black dashed curve). The red dashed curve is for ε=100 and pΔV=500 and demonstrates the shift of threshold pΔV value leading to hysteresis collapse. The interaction constant for all cases is J=145 K.
Mentions: The more complete description of ligand field action on central transition metal ion requires to consider its instantaneous behavior where time variation of field becomes relevant. In the following study, we investigate the influence of fluctuating nature of ligand field splitting energy of spin-crossover system with applied pressure on thermal curves obtained from Monte Carlo simulations. Our starting point is Hamiltonian (5) with external field (6). The detailed investigation of transition curves for pressureless system with different statistical characteristics of stochastic term, i.e., space-time correlated fluctuations is carried out in paper [14]. Based on this approach, we consider the spin-crossover system under applied pressure. The resulting transition curves are shown in Figure 4. In the presented figure, the solid black transition curves correspond to the deterministic system with interaction constant J=145 K, described by the Hamiltonian (2). The red curves is for zero pressure and fluctuations strength ε=100. This strength is the same for other transition curves obtained for pressure pΔV=100 K (blue line) and pΔV=300 K (pink line). As it was expected, the presence of white fluctuations enlarges the hysteresis [14]. The pressure action on hysteresis loop for the system with fluctuations leads to its narrowing and, similar to the fluctuationless system, shifts the cooling and heating branches toward higher temperature. It is obvious that the action of pressure and fluctuations strength is opposite, and in such a way, it is expected that for the fluctuating system, the collapse of hysteresis takes place for higher pressure.Figure 4

Bottom Line: The thermal transition accompanied by the variation of the molecular volume in nanoparticles of spin-crossover materials has been studied on the basis of microscopic Ising-like model solved using Monte Carlo methods.For considered model, we examined the spin-crossover phenomenon with applied hydrostatic pressure and thus was shown the possibility to shift transition temperature toward its room value.The obtained results of numerical simulations are in agreement with the experimental ones.

View Article: PubMed Central - PubMed

Affiliation: Department of General Physics, Chernivtsi National University, Kotsjubynskyi Str. 2, 58012, Chernivtsi, Ukraine, yugudyma@gmail.com.

ABSTRACT
The thermal transition accompanied by the variation of the molecular volume in nanoparticles of spin-crossover materials has been studied on the basis of microscopic Ising-like model solved using Monte Carlo methods. For considered model, we examined the spin-crossover phenomenon with applied hydrostatic pressure and thus was shown the possibility to shift transition temperature toward its room value. The obtained results of numerical simulations are in agreement with the experimental ones.

No MeSH data available.


Related in: MedlinePlus