A new structural material of actinium at normal pressure

Abstract

The application discloses a new actinium structure material obtained through first principle calculation and prediction, and belongs to the technical field of nuclear medical radiotherapy. The structure has an international symbol of Rm, a space group of 166, belongs to a trigonal system, a lattice constant of a=b=c=9.98371 Å, and a cell angle of α=β=γ=23.3174°. Ac1 is located at (0, 0, 0) in the cell, Ac2 is located at (0.77754, 0.77754, 0.77754), and Ac3 is located at (0.22246, 0.22246, 0.22246), thereby forming a layered hexagonal stacking structure. The structure has a low energy under normal pressure and is more stable than a traditional Fmm structure considered to be stable. Based on density functional theory calculation, the structure material has metallic properties, can be used for targeted alpha therapy, causes malignant cell death through alpha particle release, and has potential application value in the field of nuclear medical imaging and radiotherapy.

Description

Technical Field

[0001] This invention relates to the field of nuclear medicine radiotherapy technology, specifically to a method of using Fm that is more stable under normal pressure than traditionally considered. A new type of structure with a more stable m-structure, its international symbol is R. m, the structure was predicted through first-principles calculations, belongs to the trigonal crystal system, and exhibits a layered hexagonal stacked structure. Background Technology

[0002] Nuclear medicine is a discipline with applications that can serve two distinct purposes: imaging, visualizing the distribution of radionuclides within an organism, or therapy, specifically irradiating malignant cells. Regardless of the intended application, it is primarily based on drug administration defined as radiopharmaceuticals. These radiotracers typically consist of a radioactive component (the unit involving the radionuclide), whose radiation allows it to locate (gamma or beta+ emitters) or destroy target cells (alpha, beta, or Auger electron emitters), and a molecule that carries it to the target. Unlike imaging, which uses radionuclides to emit highly penetrating radiation, radiotherapy tends to use radiation that interacts strongly with matter, resulting in low-penetration radiation. In this case, the use of alpha, beta, or Auger electron emitters leads to the death of malignant cells.

[0003] Actinium is the first element in the actinide series. Of its 32 known isotopes, only 228Ac and 227Ac occur naturally as part of the decay chains of 232Th and 235U, respectively. 227Ac is the most abundant isotope, exhibiting a long half-life of 21.7 years, decaying primarily via β-emission. 228Ac is also a β-emitter, which is very rare. 225Ac possesses characteristics that make it a promising candidate for nuclear medicine applications. Its half-life is 9.9 days. Its decay follows a six-step decay chain to reach a stable nucleus, and the production of multiple α particles, compared to other α-emitters, contributes to its potential cytotoxicity.

[0004] The international symbol for the currently predicted publication is Fm. The structures of two actinium materials, m and P63 / mmc-A, are noteworthy. Both materials were predicted using first-principles calculations, and Fm... m has been successfully synthesized experimentally, fully demonstrating the guiding role of theoretical calculations in the discovery of new structures.

[0005] First-principles calculations are an effective means of predicting novel structural materials. Based on density functional theory (DFT) and electro-acoustic coupling theory, the crystal structure, electronic properties, and mechanical properties of materials can be predicted before synthesis, providing theoretical guidance for experimental synthesis.

[0006] Although Fm has already been predicted There are two actinium structures, m and P63mmc-A, but both structures can only exist stably under certain conditions, which means they are still not stable enough, which severely limits their practical application.

[0007] Therefore, the discovery of a new structural material with greater stability of actinium is of great scientific significance and application value for realizing the practical application of nuclear medicine radiotherapy technology. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the purpose of this invention is to provide an Fm that is more stable than traditionally considered at 0 GPa. A new structure R with a more stable m-structure The structure, m, was obtained through first-principles calculations and predictions, exhibiting good stability and potential practical value. To achieve the above objectives, this invention provides the following technical solution: A novel structural material of actinium, its international symbol is R. m, crystal structure parameters are as follows: Space group: 166 (trigonal crystal system) Lattice constants: a = b = c = 9.98371 Å Cell angles: α = β = γ = 23.3174° Atomic coordinates (fractional coordinates): Ac1 is located at (0, 0, 0) Ac2 is located at (0.77754, 0.77754, 0.77754). Ac3 is located at (0.22246, 0.22246, 0.22246). Beneficial effects

[0009] Compared with the prior art, the present invention has the following significant advantages: 1. At 0 GPa, with the successfully synthesized Fm Compared to the m-structure, this structure has lower energy, meaning it has better stability. 2. Phonon dispersion curves confirm that the structure does not have imaginary frequencies at ambient pressure, meaning it is thermodynamically and kinetically stable at ambient pressure. 3. Ac has a half-life of 9.9 days, and its decay follows a six-step decay chain to reach a stable nucleus. Compared with other alpha emitters, the production of multiple alpha particles contributes to its potential cytotoxicity. 4. Compared to the gamma emission of some daughter nuclides of Ac (such as 221Fr or 213Bi), radiotherapy through this structure offers the possibility of tracking it after injection; 5. Based on first-principles calculations and predictions, the electronic structure is clearly defined, providing a clear direction for experimental synthesis; 6. It can be applied to fields such as imaging and radiotherapy. Attached Figure Description

[0010] Figure 1 The new R proposed in this invention A schematic diagram of the crystal structure of the m-structure under normal pressure. It is a trigonal crystal system, forming a layered hexagonal stacked structure. The crystal structure is presented in VESTA software.

[0011] Figure 2 For R The band structure and electronic density of states diagrams for the m-structure are shown. Green represents the band and projected density of states contributed by the s orbitals, blue represents the band and projected density of states contributed by the p orbitals, and red represents the band and projected density of states contributed by the d orbitals.

[0012] Figure 3 The phase diagrams for various Ac structures predicted by first-principles calculations are shown.

[0013] Figure 4 For R Phonon dispersion curves of the m-structure. Detailed Implementation

[0014] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments are based on first-principles calculations and will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way.

[0015] First-principles calculations based on density functional theory (DFT) were performed using the VASP software package. The exchange correlation potential used in the calculations was the Perdew-Burke-Ernzerhof (PBE) approximation under the generalized gradient approximation (GGA). The kinetic energy cutoff of the plane wave basis set was set to 600 eV, and the electron energy converged to at least 1 × 10⁻⁶ eV. 6 eV, with all force components relaxed to at least 2 meV / Å. Self-consistent field (SCF) calculations were performed using an 11×11×11 Monkhorst–Pack k-point grid. Phonon calculations based on Density Functional Perturbation Theory (DFPT) were performed using a 2×2×2 q-point grid.

[0016] like Figure 1 As shown, this structure exhibits typical R In the m-structure, actinium atoms are densely packed in layers along the

[111] direction, forming an anisotropic two-dimensional layered framework. The atoms within each layer are hexagonally close-packed, exhibiting a hexagonal layered stacking structure. There is a specific interlayer coupling effect between adjacent actinium atom layers, forming a rhombohedral arrangement.

[0017] like Figure 2 As shown, the calculated band structure and density of states diagram are obtained. Green represents the band structure and projected density of states contributed by the s orbitals, blue represents the band structure and projected density of states contributed by the p orbitals, and red represents the band structure and projected density of states contributed by the d orbitals. The gray dotted lines represent the Fermi levels. A density of states exists at the Fermi levels, exhibiting metallic properties.

[0018] like Figure 3 As shown, the pressure-induced phase diagrams of various Ac structures predicted by first-principles calculations show that, at 0 GPa, R... The energy ratio of the m phase to Fm The m phase has lower energy, meaning that R under normal pressure... m ratio Fm m is more stable.

[0019] like Figure 4 As shown, R was obtained through calculation. The phonon dispersion relation of m at normal pressure shows that no imaginary frequency appears in the phonon dispersion diagram, indicating that the structure is thermodynamically and kinetically stable at normal pressure.

Claims

1. A novel structure of actinium obtained through first-principles calculations and predictions, characterized in that, The international symbol is R m belongs to the trigonal crystal system and exhibits a layered hexagonal stacked structure.

2. The novel structure of actinium according to claim 1, characterized in that, The crystal structure parameters of the structure at 0 GPa are: Space group: 166 (trigonal crystal system) Lattice constants: a = b = c = 9.98371 Å Cell angles: α = β = γ = 23.3174°.

3. The novel structure of actinium according to claim 2, characterized in that, The atomic fractional coordinates of the structure are: Ac1 is located at (0, 0, 0) Ac2 is located at (0.77754, 0.77754, 0.77754). Ac3 is located at (0.22246, 0.22246, 0.22246).

4. The novel structure of actinium according to any one of claims 1-3, characterized in that, At 0 GPa, the structure is more stable than the traditionally considered Fm. The m-structure is more stable.

5. The application of a novel actinium structure according to any one of claims 1-4 in targeted α therapy.

6. The application according to claim 5, characterized in that, The targeted alpha therapy refers to the use of radiation therapy, which tends to use radiation that interacts strongly with matter, resulting in low penetration. In this case, the use of alpha particles leads to the death of malignant cells.

7. The application of a novel actinium structure according to any one of claims 1-6 in targeted α therapy under normal pressure.

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