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采用基于密度泛函理论的第一性原理平面波超软赝势方法，在广义梯度近似下，研究了W20O58晶胞、W20O58（010）表面结构及其氢吸附机理.计算结果表明：W20O58晶体理论带隙宽度为0.8 eV，为间接带隙，具有金属性.W20O58晶体中W–O共振较强，以共价键居多.W20O58（010）表面有WO终止（010）表面和O终止（010）表面，表面结构优化后使得W–O键长和W–O–W键角改变，从而实现表面弛豫.分别计算了H2分子吸附在WO终止（001）表面和O终止（001）表面的WO-L-O1c，WO-V-O1c，WO-L-O2c，WO-V-O2c，O-L-O1c和O-V-O1c六种吸附构型，其中WO-L-O1c，WO-V-O1c和WO-L-O2c这三种吸附构型不稳定；而WO-V-O2c，O-L-O1c和O-V-O1c这三种吸附构型都很稳定，H2分子都解离成两个H原子，吸附能均为负值，分别为-1.164，-1.021和-3.11 eV.WO-V-O2c吸附构型的两个H原子分别吸附在O和W原子上；O-L-O1c吸附构型的两个H原子，一个与O原子成键，另一个远离了表面.其中O-V-O1c吸附构型最稳定，两个H原子失去电子，为O原子提供电子.分析其吸附前后的态密度，H的1s轨道电子与O的2p，2s轨道电子相互作用，均形成了一些较强的成键电子峰，两个H原子分别与O1c形成化学键，最终吸附反应生成了一个H2O分子，同时产生了一个表面氧空位.With the development of modern industrial technology, tungsten products prepared from traditional tungsten powder cannot meet the demands of industry. However, the properties of tungsten products produced from ultra-fine tungsten powder have been greatly improved:they have high strength, high toughness, and low metal plasticity-brittle transition temperature. Hence, it is necessary to carry out theoretical research of the micro-adsorption dynamics during hydrogen reduction of W20O58, which is beneficial to synthetizing ultra-fine tungsten powder. In this article, to comprehend the crystal characteristics of W20O58 (010) surface and provide the theoretical reaction law for hydrogen reduction on W20O58 (010) surface, the absorption mechanism of H2 molecule on W20O58 (010) surface is studied by the first-principles calculation based on density functional theory in a plane wave pseudo-potential framework. The results show that the indirect band gap of W20O58 is 0.8 eV, indicating that it has metallic characteristic. The W20O58 (010) surface has different terminations, i.e., WO-terminated (010) surface and O-terminated (010) surface. After the geometrical optimization of the two surfaces, the W–O bond length and bond angle of W–O–W are both changed. In addition, six absorption configurations of H2 on W20O58 (010) surface, including WO-L-O1c, WO-V-O1c, WO-L-O2c, WO-V-O2c, O-L-O1c and O-V-O1c, are chosen to be investigated. The calculation results show that the WO-L-O1c, WO-V-O1c and WO-L-O2c absorption system are unstable, while the WO-V-O2c, O-L-O1c and O-V-O1c absorption configuration are stable. When H2 molecule is dissociated into two H atoms, the absorption energies of the three stable configurations are-1.164 eV,-1.021 eV and-3.11 eV, respectively. It is obvious that the O-V-O1c absorption configuration is the most stable one. The analysis of density of states reveals that the 1s state of H atom interacts with the 2p and 2s states of O atom. The outermost O1c atom of O-terminated (010) surface contains an unsaturated bond, which results in the formation of bonding between two H atoms and O1c atom. As a result, an H2O molecule is formed and an oxygen vacancy on the surface is generated after absorption reaction. By combining experimental observations with simulation calculations, the mechanism of hydrogen reduction of W20O58 can be revealed from a microscopic view.
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Keywords:
- first-principles calculations /
- W20O58 /
- H2 /
- absorption energy
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[25] Segall M D, Lindan P J D, Probert M J, Pickard C J, Hasnip P J, Clark S J, Payne M C 2002 J. Phys.: Condens. Matter 14 2717
[26] Wang Y, Perdew J P, Chevary J A, Macdonald L D, Vosko S H 1990 Phys. Rev. A 41 78
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[28] Monkhorst H J, Pack J D 1976 Phys. Rev. B 13 5188
[29] Fletcher R 1970 Comput. J. 13 317
[30] Setyawan W, Curtarolo S 2010 Comput. Mater. Sci. 49 299
[31] Yamaguchi O, Tomihisa D, Kawabata H, Shimizu K 1987 J. Am. Ceram. Soc. 70 94
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[1] Peng W Z 2004 Cemented Carbide 21 142 (in Chinese) [彭卫珍 2004 硬质合金 21 142]
[2] Fu X M 2004 Shanghai Nonferrous Met. 25 149 (in Chinese) [傅小明 2004 上海有色金属 25 149]
[3] Wu X D, Chai Y X, Fu X M, Fu M X, Dai Q X 2005 Chinese J. Rare Met. 29 570 (in Chinese) [吴晓东, 柴永新, 傅小明, 傅明喜, 戴起勋 2005 稀有金属 29 570]
[4] Wang G, Li H H, Huang Z W, Chen M H, Wang Q K, Zhong W L 2009 Rare Metal. Mat. Eng. 38 548 (in Chinese) [王岗, 李海华, 黄忠伟, 陈美华, 王庆康, 钟伟良 2009 稀有金属材料与工程 38 548]
[5] Liao J Q, Huang Z F, L H B, Chen S Y, Zou Z Q 2000 J. Cent. South Univ. Technol. 31 51 (in Chinese) [廖寄乔, 黄志锋, 吕海波, 陈绍衣, 邹志强 2000 中南工业大学学报 31 51]
[6] Wang Z X, Shu D X, Tang X H 1993 Eng. Chem. Metall. 14 224 (in Chinese) [王志雄, 舒代萱, 唐新和 1993 化工冶金 14 224]
[7] Wu X D, Chai Y X, Fu M X 2005 Cemented Carbide 22 65 (in Chinese) [吴晓东, 柴永新, 傅明喜 2005 硬质合金 22 65]
[8] Li H K, Yang J G, Li K 2010 Tungsten Metallurgy (Changsha: Central South University Press) pp36-39 (in Chinese) [李洪桂, 羊建高, 李昆 2010 钨冶金学 (长沙: 中南大学出版社) 第36--39页]
[9] Yu G, Han Q G, Li M Z, Jia X P, Ma H A, Li Y F 2012 Acta Phys. Sin. 61 040702 (in Chinese) [于歌, 韩奇钢, 李明哲, 贾晓鹏, 马红安, 李月芬 2012 物理学报 61 040702]
[10] Qiu K Q, Wang A M, Zhang H F, Qiao D C, Ding B Z, Hu Z Q 2002 Acta Metall. Sin. 38 1091 (in Chinese) [邱克强, 王爱民, 张海峰, 乔东春, 丁炳哲, 胡壮麒 2002 金属学报 38 1091]
[11] Hua J S, Jing F Q, Dong Y B, Tan H, Shen Z Y, Zhou X M, Hu S L 2003 Acta Phys. Sin. 52 2005 (in Chinese) [华劲松, 经福谦, 董玉斌, 谭华, 沈中毅, 周显明, 胡绍楼 2003 物理学报 52 2005]
[12] Tan J, Zhou Z J, Zhu X P, Guo S Q, Qu D D, Lei M K, Ge C C 2012 Trans. Nonferrous Met. Soc. China 22 1081
[13] Liu H M, Fan J L, Tian J M, You F 2009 China Tungsten Ind. 24 29 (in Chinese) [刘辉明, 范景莲, 田家敏, 游峰 2009 中国钨业 24 29]
[14] Hessel S, Shpigler Β, Botstein O 1993 Rev. Chem. Eng. 9 345
[15] Wu X W, Luo J S, Lu B Z, Xie C H, Pi Z M, Hu M Z, Xu T, Wu G G, Yu Z M, Yi D Q 2009 Trans. Nonferrous Met. Soc. China 19 785
[16] Xu L, Yan Q Z, Xia M, Zhu L X 2013 Int. J. Refract. Met. Hard Mater. 36 238
[17] Yu Y X 2013 Phys. Chem. Chem. Phys. 15 16819
[18] Yu Y X 2016 J. Phys. Chem. C 120 5288
[19] Yang G M, Xu Q, Li B, Zhang H Z, He X G 2015 Acta Phys. Sin. 64 127301 (in Chinese) [杨光敏, 徐强, 李冰, 张汉壮, 贺小光 2015 物理学报 64 127301]
[20] Xue L, Ren Y M 2016 Acta Phys. Sin. 65 156301 (in Chinese) [薛丽, 任一鸣 2016 物理学报 65 156301]
[21] Yu Y X 2014 ACS Appl. Mater. Interfaces 6 16267
[22] Li B, Wu T Q, Wang C C, Jiang Y 2016 Acta Phys. Sin. 65 216301 (in Chinese) [李白, 吴太权, 汪辰超, 江影 2016 物理学报 65 216301]
[23] Chen J, Lu D Y, Zhang W H, Xie F Y, Zhou J, Gong L, Liu X, Deng S Z, Xu N S 2008 J. Phys. D: Appl. Phys. 41 115305
[24] Lu D Y, Chen J, Deng S Z, Xu N S, Zhang W H 2008 J. Mater. Res. 23 402
[25] Segall M D, Lindan P J D, Probert M J, Pickard C J, Hasnip P J, Clark S J, Payne M C 2002 J. Phys.: Condens. Matter 14 2717
[26] Wang Y, Perdew J P, Chevary J A, Macdonald L D, Vosko S H 1990 Phys. Rev. A 41 78
[27] Perdew J P, Chevary J A, Vosko S H, Jackson K A, Pederson M R, Singh D J 1992 Phys. Rev. B 46 6671
[28] Monkhorst H J, Pack J D 1976 Phys. Rev. B 13 5188
[29] Fletcher R 1970 Comput. J. 13 317
[30] Setyawan W, Curtarolo S 2010 Comput. Mater. Sci. 49 299
[31] Yamaguchi O, Tomihisa D, Kawabata H, Shimizu K 1987 J. Am. Ceram. Soc. 70 94
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