Structural Order and Dielectric Behaviour of Hydroxyapatite

Tofail, Syed A. M.; Haverty, D.; Stanton, Kenneth T.; McMonagle, J.B.

doi:10.1080/00150190590965523

Cited by 68 publications

(64 citation statements)

References 15 publications

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“…These results are comparable with the data obtained by other authors [10,21] and are very close to the data from [22]. Comparison of the calculated value of the forbidden energy band Eg ~ 4.6 eV [32,33,35], with other data computed show that all Eg data are very close to the data obtained in [35]: Eg ~ 5.4 eV from Calderin and Scott [9], Eg ~ 5.23 eV from Slepko and Demkov [22], Eg ~ 4.51 eV from Rulis et al [26].…”

Section: Infinite Periodical Lattice and Electrical Potentialsupporting

confidence: 83%

“…The upper right DOS image in Fig. 12 presents the DOS structure for the initial pure hexagonal HAP, and consists of several peaks (A, B, C and D) in the valence band, as well as several deep levels [35], which is in good agreement with the data obtained by other authors [10,[22][23][24][25][26] and corroborated by recent experimental data obtained by synchrotron technique [33,34].…”

Section: Hap Crystal With Defects (O H Oh Vacancies H Interstitialsupporting

confidence: 81%

“…-the electron energy band structures of initial HAP clusters computed by PM3 methods correspond well to the data reported (both experimental and simulated) [10,21,22,26,41,42,47] (see more details in [30] and in Table 4) -the main values obtained for the energy gap are Eg ∼ 3.54 eV for fixed PC (C3 symmetry), Eg ∼ 4.56 eV for relaxed PC (C1 symmetry) as compared with known data Eg ∼ 4.43 eV for the last structure in [41,42], and Eg ∼ 5.41 eV for the smallest HAP (C1 symmetry) as compared with Eg ∼ 5.38 eV for fixed HAP bulk [42]; -the computed data show some variations of the energies of the electronic band structures (E HOMO and E LUMO) with the addition of hydrogen atoms and corresponding variations of Eg (4.02-5.56 eV, see Table 4), and have a tendency for a decrease of Eg at the finally filled hydrogen bonds -all these data are in good agreement with the experimentally measured Eg ∼ 4.0 eV for a surface charged HAP samples in [47]; -the change of the total dipole moment and polarization are varied with increase of added hydrogen, but average values slightly decrease as compared with the initial state (see Table 3, Table 4). These results are very urgent for practical applications, because recent studies of the influence of electrical charge on HAP specimens surface on the osteoblast behavior and bone tissue growth clearly show that the deposition on the HAP surface of a negative charge enhances attachment and proliferation of the osteoblasts and fabrication of the bone tissue [36][37][38][39][40].…”

Section: Main Features Of Electrical Field Charges and Potential Inssupporting

confidence: 61%

“…It has specific structural features that define its basic physical properties, charge distribution and surface electric potential, which have especially important role for the living cells adhesion and proliferation [1][2][3]. The specific feature of HAP is that it has a selected direction of the formation of hydroxyl OH groups (inner OH-channels) along the c axis, which allows the transfer of protons along this axis under special conditions [4][5][6][7][8][9][10][11][12][13][14][15]. Special interest here is connected with the physical properties of the nanosized HAP clusters [12][13][14][15][16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

“…The surface charge σ = P creates the electric field Eel = σ/(2εε0) = P/(2εε0) ∼ (0.28-0.295) × 10 9 V/m, for ε = 1, where ε is the relative dielectric permittivity of the media, and ε0 = ε0 ≈ 8.85 × 10 −12 F/m. For our estimation we took the average value of ε = 10 (are several reports in HAP on ε from 5 up 15 [7,10,30,44]). In this case an electrical field exists inside the HAP NP must be: Eel ∼ (0.28 -0.30) × 10 8 V/m, appearing as a result of surface charges, which can shift all the NP energy levels, including the surface level and work function, and this shift must depended on the NP size values.…”

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confidence: 99%

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Компьютерные Исследования Наноструктур Гидроксиапатита, Их Особенности И Свойства

Bystrov¹

2017

Math.Biol.Bioinf.

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Abstract. In this review paper the main approaches to modeling the hydroxyapatite (HAP) structures and first-principle calculations of their properties, pure and with various defects, are considered. First, the HAP nano-particles (NPs) and clusters peculiarities are described using different methods: molecular mechanical and quantum mechanical, especially semi-empirical such as PM3. Both approximations used here, namely, restricted Hartee-Fock (RHF) and unrestricted Hartee-Fock (UHF), are considered. The influence of the protons (hydrogens), contained in the surrounding medium (pH), on the formation of HAP nanoparticles of various sizes and shapes is considered and discussed. Second, the HAP crystal unit cells studies are considered on the basis of a density functional theory (DFT) modelling. The main peculiarities of both phases (hexagonal and monoclinic) are considered too, including their ordered and disordered substructures. One of the important aspects of the computer modeling of HAP is to build the models and consider various structural modifications of HAP (such as, vacancies of oxygen atoms and hydroxyl OH group, hydrogen interstitials and different substitutions of atoms in HAP unit cell), which allow explicitly creating and exploring the changes in the charges of HAP and the electrical potential on the HAP surface. HAP modifications are most close to biological HAP and therefore are necessary for implant medical applications and can create and functionalize HAP surface with most adhesive properties for living cells (osteoblasts, osteoclatst). This improves the HAP implant quality. Besides, it has recently been established that oxygen vacancy in HAP influences their photo-catalytic properties. It is important for HAP usage as in environmental remediation and for bacteria inactivation. Therefore it is very important to create and investigate the oxygen vacancy models in HAP, and others defects models. In this work we review a DFT modelling and studies of HAP, both pure perfect bulk and imperfect bulk cases. Special HAP modelling approaches are used for layered slab super-cells units, which include vacuum spaces between the layered slabs forming HAP surface. To all these computer studies the first principle calculations were applied. In this review various DFT approximations are analysed for bulk and surface modified HAP. These approximations are carried out using both the local basis (local density approximation -LDA, in AIMPRO codes) and the plane-waves (generalized gradient approximation -GGA, in VASP codes). Data of all structures and models of HAP defects investigated are widely analyzed.

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Section: Infinite Periodical Lattice and Electrical Potentialsupporting

confidence: 83%

Section: Hap Crystal With Defects (O H Oh Vacancies H Interstitialsupporting

confidence: 81%

Section: Main Features Of Electrical Field Charges and Potential Inssupporting

confidence: 61%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Компьютерные Исследования Наноструктур Гидроксиапатита, Их Особенности И Свойства

Bystrov¹

2017

Math.Biol.Bioinf.

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Electrical Functionalization and Fabrication of Nanostructured Hydroxyapatite Coatings

Bystrov

Bystrova

Dekhtyar

et al. 2019

Bioceramics and Biocomposites

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Functional Surfaces for Biomaterials

Nagai

Horiuchi

Nakamura

et al. 2017

Handbook of Solid State Chemistry

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Material surfaces and biological systems form interfaces that are metastable and change depending on circumstances. The preferable properties of the biomaterial surface are described by the term of biocompatibility. However, the desirable properties vary widely depending on the applications. Surface chemistry, surface topology, mechanical properties, and electric properties are representative key factors involved in the surface properties of biomaterials. This chapter focuses especially on electric properties of the biomaterials. Hydroxyapatite, the most well‐known inorganic biomaterial, can be electrically polarized by an electrical procedure. The surface properties, the wettability, and surface free energy, are changed by the polarization, and the polarization influences cultured cell behavior and biomimetic crystallization processes on the surfaces.

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Structural Order and Dielectric Behaviour of Hydroxyapatite

Cited by 68 publications

References 15 publications

Компьютерные Исследования Наноструктур Гидроксиапатита, Их Особенности И Свойства

Компьютерные Исследования Наноструктур Гидроксиапатита, Их Особенности И Свойства

Electrical Functionalization and Fabrication of Nanostructured Hydroxyapatite Coatings

Functional Surfaces for Biomaterials

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