Abstract:Water absorption in the metal-organic framework (MOF) material Cu-BTC, up to a concentration of 3.5 H2O per Cu ion, is studied via density functional theory at the meta-GGA+U level. The stable arrangements of water molecules show chains of hydrogen-bonded water molecules and a tendency to form closed cages at high concentration. Water clusters are stabilized primarily by a combination of water-water hydrogen bonding and Cu-water oxygen interactions. Stability is further enhanced by van der Waals interactions, … Show more
“…One must keep in mind that the results of this work will tend to show overbinding of the np structure with respect to the lp one; but at fixed volume, one expects interactions involving water to be reasonably accurate. Figure 2.Comparison of enthalpy vs. volume of dry MIL-53(Cr) using an ad hoc parameterization of DFT at the MGGA level (PBEsol + RTPSS + D3(BJ) + U + J) (Cockayne and Nelson, 2015; Cockayne, 2017) and a MGGA that has been benchmarked across different systems (TPSS + D3(BJ) + U + J) (Brandenburg et al ., 2016). …”
Section: Resultsmentioning
confidence: 99%
“…Comparison of enthalpy vs. volume of dry MIL-53(Cr) using an ad hoc parameterization of DFT at the MGGA level (PBEsol + RTPSS + D3(BJ) + U + J) (Cockayne and Nelson, 2015; Cockayne, 2017) and a MGGA that has been benchmarked across different systems (TPSS + D3(BJ) + U + J) (Brandenburg et al ., 2016). …”
Section: Resultsmentioning
confidence: 99%
“…Instead, dispersion-corrected MGGA functionals are required to get the proper balance of forces necessary to accurately model water interactions (Pestana et al, 2017). In previous work (Cockayne and Nelson, 2015;Cockayne, 2017), we were able to reproduce benchmarking energies and geometries of small water clusters quite well by using a combination of a PBEsol (Perdew et al, 2008) gradient term, the RTPSS MGGA density functional (Perdew et al, 2009;Sun et al, 2011), empirical van der Waals forces at the Grimme D2 level (Grimme, 2006), and a Hubbard U value of 7.05 for the water oxygen, but the combination of parameters that we chose was admittedly ad hoc and not derived self-consistently. In this work, we seek a more transferable density functional, one that has been benchmarked across different systems in the literature.…”
We use density functional theory meta-generalized gradient approximation TPSS + D3(BJ) + U + J calculations to investigate the energetics and geometry of water molecules in the flexible metal-organic framework material Materials of Institut Lavoisier (MIL)-53(Cr) as a function of cell volume. The critical concentration of water to cause the transition from the large pore (lp) to the narrow pore (np) structure is estimated to be about 0.13 water molecule per Cr. At a concentration x = 1 water molecule per Cr, the zero-temperature np and lp configurations each have a hydrogen bond between the H of each framework hydroxyl group and water oxygen (OW). At intermediate volumes, water dimer-like configurations are observed. A concentration x = 1.25 leads to hydrogen bonding between water molecules in the np phase that is absent for x = 1. Our results suggest possible mechanisms for pore closing in hydrated MIL-53(Cr).
“…One must keep in mind that the results of this work will tend to show overbinding of the np structure with respect to the lp one; but at fixed volume, one expects interactions involving water to be reasonably accurate. Figure 2.Comparison of enthalpy vs. volume of dry MIL-53(Cr) using an ad hoc parameterization of DFT at the MGGA level (PBEsol + RTPSS + D3(BJ) + U + J) (Cockayne and Nelson, 2015; Cockayne, 2017) and a MGGA that has been benchmarked across different systems (TPSS + D3(BJ) + U + J) (Brandenburg et al ., 2016). …”
Section: Resultsmentioning
confidence: 99%
“…Comparison of enthalpy vs. volume of dry MIL-53(Cr) using an ad hoc parameterization of DFT at the MGGA level (PBEsol + RTPSS + D3(BJ) + U + J) (Cockayne and Nelson, 2015; Cockayne, 2017) and a MGGA that has been benchmarked across different systems (TPSS + D3(BJ) + U + J) (Brandenburg et al ., 2016). …”
Section: Resultsmentioning
confidence: 99%
“…Instead, dispersion-corrected MGGA functionals are required to get the proper balance of forces necessary to accurately model water interactions (Pestana et al, 2017). In previous work (Cockayne and Nelson, 2015;Cockayne, 2017), we were able to reproduce benchmarking energies and geometries of small water clusters quite well by using a combination of a PBEsol (Perdew et al, 2008) gradient term, the RTPSS MGGA density functional (Perdew et al, 2009;Sun et al, 2011), empirical van der Waals forces at the Grimme D2 level (Grimme, 2006), and a Hubbard U value of 7.05 for the water oxygen, but the combination of parameters that we chose was admittedly ad hoc and not derived self-consistently. In this work, we seek a more transferable density functional, one that has been benchmarked across different systems in the literature.…”
We use density functional theory meta-generalized gradient approximation TPSS + D3(BJ) + U + J calculations to investigate the energetics and geometry of water molecules in the flexible metal-organic framework material Materials of Institut Lavoisier (MIL)-53(Cr) as a function of cell volume. The critical concentration of water to cause the transition from the large pore (lp) to the narrow pore (np) structure is estimated to be about 0.13 water molecule per Cr. At a concentration x = 1 water molecule per Cr, the zero-temperature np and lp configurations each have a hydrogen bond between the H of each framework hydroxyl group and water oxygen (OW). At intermediate volumes, water dimer-like configurations are observed. A concentration x = 1.25 leads to hydrogen bonding between water molecules in the np phase that is absent for x = 1. Our results suggest possible mechanisms for pore closing in hydrated MIL-53(Cr).
“…The nonzero U of oxygen greatly reduces the residual forces, while the value of U for Cu ions controls the splitting in the Cu d levels, which have a great effect on calculated bandgap [59].…”
Section: Density Functional Calculations -Recent Progresses Of Theorymentioning
confidence: 99%
“…• The Cu-BTC [58], a material consisting of copper dimers linked by 1,3,5-benzenetricarboxylate C 6 O 9 H 3 (BTC) units, was studied for its ability to absorb up to 3.5 H 2 O per Cu as the Cu binds to the closest oxygen of the water molecule [59]. The U parameter in the meta-GGA+U calculation of the Cu-BTC was adjusted with the experimental crystallographic structure and the bandgap by minimizing the absorption at 2.3 eV.…”
Section: Density Functional Calculations -Recent Progresses Of Theorymentioning
This chapter introduces the Hubbard model and its applicability as a corrective tool for accurate modeling of the electronic properties of various classes of systems. The attainment of a correct description of electronic structure is critical for predicting further electronic-related properties, including intermolecular interactions and formation energies. The chapter begins with an introduction to the formulation of density functional theory (DFT) functionals, while addressing the origin of bandgap problem with correlated materials. Then, the corrective approaches proposed to solve the DFT bandgap problem are reviewed, while comparing them in terms of accuracy and computational cost. The Hubbard model will then offer a simple approach to correctly describe the behavior of highly correlated materials, known as the Mott insulators. Based on Hubbard model, DFT+U scheme is built, which is computationally convenient for accurate calculations of electronic structures. Later in this chapter, the computational and semiempirical methods of optimizing the value of the Coulomb interaction potential (U) are discussed, while evaluating the conditions under which it can be most predictive. The chapter focuses on highlighting the use of U to correct the description of the physical properties, by reviewing the results of case studies presented in literature for various classes of materials.
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